1) To make combat hacking possible you need targets, possibilities and speed. 5 rounds of wifi scanning and hacking on the fly vs 1 complex FA action does not work. SR4 used extended tests for hacking and wifi scanning, which was acceptable before the combat, but not during the combat. Kill extended tests, adjust needed successes, make it complex actions. You can use something like marks or note down hits etc, but basically its like the normal combat sequence: attack, defense, soak with combat superiority for very short time. Lets assume just as an idea that hacking on the fly can give you admin access for a short time (and that you would need probing for permanent access).
2) In my world a Tactical Network has become the default instrument for almost anything team related. Almost everyone of my NPCs have it, from normal guards to sport teams, from firefighters to soliders, from low end runnres to high end SEALS. Of course the rating is different, from rating 0 to 4, depending on situation, software and hardware. Give every archetype in the book a low level to mid level tacnet per default, from ganger to street sam. It should be descriped as normal as a smartlink, gas mask, armor jacked or fake SIN. You are a a runner, it is assumed that you have a fake SIN, an armor jacked and a tacnet. To get a full benefit it must be DNI controlled, manually controlled tacnets only give half the bonuses.
3) In my world, many people use airborne micro/mini drones. Sport teams, firefighters, cops, runner, soldiers, reporters etc. Almost everyone who can profit from an air view invests these 1-2k Ĩ for some of these drones (air, ground, whatever). They have the same status as guns, smartlinks, armor jackets etc. If you meet an enemy, you can safely assume that is has slaved a fly spy to his level 1 tacnet. This of course must be reflected in the archetypes and in the item description.
4) Radio communication. Even the most dedicated Eloka-Ninja-Team will use radio communication (often combined with data transmission) from time to time. Many professional teams use them constantly, dedicating their life on their hacker, encryption and hidden status.
5) There of course many people who shut down the wifi for their items for skinlink/cable/PAN range 1m wifi or internal DNI control. Fine. But usually they still have a link and that link can be online (from webpages to facebook to tacnet and radio communication). Usually that link is DNI controlled (skinlink, nanotrodes, sim modul). Usually it means that internal ware is linked to the link as well (for example for a cybernetic diagnostic suite etc). Even if you have no direct access to the cyberware you can often gain access through the link, if the link is online. If you use a decoy link that is often linked to the runner link as well (and working through it is something like bringing a 40 dice tank troggy down: possible, but it takes some actions)
6) A lot of environment works on Wifi as well, from cars to construction drones to remote pizza crawlers. Cyberpunk 2020 had a very interesting idea: with some sort of ping you immediately see all remote controlled devices online (something similar exists in SR4 and 5 (in SR4 with extended tests, which should be corrected)), and with the next action you could hack and control them for a short time. Sometimes you can simply use standard orders, in other cases you must prepare default command scripts (similar to a samurai buying different kind of ammunition) for different situation (like throw things, attack target, block target etc). You could even use low level mass hacking (bot nets, multiple agents on your link) to hack and control several low level things at the same time to achieve "matrix space superiority" against an enemy team.
7) Your target is still offline? Well, you use air burst grenades with micro transmitters splattered all over the area. Use squirt guns with micro transmitters/skinlink manipulators. Use dart guns with nano transmitters. Make the nanoware cheap and effective (the nanoware which crawls through your veins and connects to internal ware). There are many possibilities on how to forcefully connect to someone. Hackrape is real.

=> Throw that all together and a combat hacker could do some or all of the following (depending on situation, numbers etc - but then again, I write this down to give you an idea, not to replace an entire chapter in SR45).
- reduce enemy tacnet bonus from +4 to 0
- give enemy using a manipulated tacnet a malus up to -4 (combined to an 8 dice difference in combat effectiveness)
- manipulate the analytical engine of an enemy tacnet, weapon of teammates may be shown as jammed, ammunition counter shows something else, gerade explosion radii are bigger or smaller, concrete cover becomes paper cover and the other way around (or so it seems on the AR of the enemy), enemies become visible through walls (or the own people do not show up in the tacnet), their movement is predicted wrong (which leads the enemy team into a killzone). You know the stuff sadistic gamemasters and puppetmastering players love to do.
- clear up the own tacnet if hacked by an enemy hacker
- spam online commlinks with gay troll porn reducing visibility
- manipulate enemy communication and disable it or feed wrong orders (with a specialised edit-on-the-fly software) and status information ("Boss, i am bleeding out in the other alley, come to me").
- disable enemy micro drones, convert them into kamikaze distractions or use them to feed wrong information to the enemy tacnet - or increase the drone numbers for the team hacker at least temporarily.
- manipulate the environment. construction drones throw 1 ton blocks at you, car doors open suddenly when you pass, cranes are swinging at you, junk bots try to pick you up.
- take over an online link and work your way from there to linked items and cyberware.
- protect your team from enemy attacks, shut him down via electronic warfare (which could be handled a little bit like spell defense provided by a mage).
- use dedicated combat bots to kill the enemy (or convert infrastructure bots into kamikaze bots
- have fun with psychotropic or black ice in the DNI controlled link, which could give short term problems or even kill the user, depending on how far you want to go with brain hacking rules.
- depending on the linked status you could even block equipment or delay actions (clip dropping, items jammed etc), requiring a reboot, taking time, taking away enemy bonuses.
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It would mean that there are certain incentives to go online and to go online with DNI - and certain consequences if you neglect your computer/brain safety. It gives you the possibility to go offline and it gives you the possibility to go online without looking as an idiot to any sane human. Combat hacking becomes a natural part of combat: you can be online, but you loose a lot of advantages, and you circumvent other dangers, which is exactly the basic idea behind combat hacking. I assume that many people have no problems with imagining "there is a micro drone in the air tracking my movement, I will hack and manipulate its data feed to the enemy tacnet"), as it seems far more embedded in the sixth world as ... online silencers.
Online silencers.
Online knifes
Online stealth suites
Online air seal
Online batons
Online air tank
Online finger comparment.
*sigh*
Edit: one common counter argument was: a tacnet is too powerful, compared to the costs or difficulty involved. To that I can only answer: so? An Ares Alpha, amor jacked or medkit is very powerful compared to the investment, too and no one really complains. If a tacnet becomes so normal and integrated into the world then it will be the same as a smartlink: standard. That is nothing to be afraid and it has happened before in all editions. And of course: it is just a concept, an idea how it could worked. I really donīt care if it would be +4 or +8 oder +2 in the end.
SYL