I have been asked to play in a slight more advanced group (400BP + 100 karma and 150.000 nuyen), and I was thinking of borrowing an idea from Babylon 5 and creating a Techno-Mage.

Techno-Mages are people who hide their significantly high technology abilities behind a mask of mysticism and trickery, and for some reason I was thinking that such a character would make for a very interesting Shadow Runner.

But at the same time I was baffled by what such a trickster character who acts like a Magician of technology would need.

So, dumpshockers, I thought I'd pick your brain.

Lots and lots of microdrones come to mind. Also creative use of AR Editing.

cyber shotgun with fireball rounds.

how hard would it be to get discreet holo/trideo projectors to mimic illusion spells.

thats all i can think of right now. i once made a street sammy that had various ware to mimic mages/adepts.

Talk with your GM if you can take that AR-Concealment Critter Power as an Echo.

Techno-mage
1. loads of specialized cyberware
2. probably rigging and hacking skills, not necessarily a technomancer
3. heavily customized gear
4. one hell of a comm unit cluster with holo/ar projector

You want a Technomancer. Via drones or echoes, they do stuff that nobody else can, and thanks to that starting karma boost, they get their fancy toys off the bat. Its important to keep in mind that a technomancer can use any toys a regular hacker can, from skinwebs to satlinks and agents. If you're pretending to be a regular hacker, having a few regular agents and the ware to run them might not be a bad thing, especially since you can only have one unregistered sprite out at any given time. Might want to look at the unwired optional rules for learning echoes without initiating.

Likely echoes
E-sensing. Its like assensing for electronics and bioelectric fields
Multiprocessing: being able to be in multiple nodes at once, and not suck at it.
Mesh Reality: an upgrade to multiprocessing, it basically lets you be dual natured for the matrix and meat space at the same time, while VRing, using our matrix initiative and (some) passes in meatspace.
Skinlink: It works like a skinlink, you can interface with devices by touch - except that it doesn't need a reciever. You can connect with anything you can touch.
Resonance Trodes: An upgrade to skinlink, you can use your touch to work as trodes on other people, even unwillingly with an unarmed grapple. With the ability to Thread program options for complex forms at will - such as psychotropic for blackout - this means you can brainwash people with a mere touch.
Biowire: You, yourself, can fake being a skillwire system at your submersion grade. However, you have to use threading to adapt existing skillsofts. Once you do so, you can run them as usual - or learn it as a CF with karma. While I believe you can't thread new options for it on the fly, you can use sprites to temporarily boost it, or near-permanently via linking.
Sparky: lets you cause critical failures and even hardware damage against mundane equipment in cybercombat.

You want Jury Rigging quality, minimum. It lets you do odd, over the top custom stuff with machinery.
Type-O system. For a bio-mancer technomancer. Give up one point of resonance for some bioware and you can make a rather effective samurai, the idea being that this isn't a 'stay at home' or 'zonk out in the car' hacker, but someone who can walk with the rest of the team and kick just as much ass -in person, while tearing someone a new on on the matrix at the same time.

Just what occured to me off the top of my head. Hope that helps. Look at unwired. There's some neat stuff in there you could use for this concept.

i can't help feeling that being a technomancer for a character that is flashy and highly visible sounds like a spectacularly bad idea. sure, you'll be able to do things that no one else can. also, there are people out there who look for people like you so that they can vivisect you and try to figure out what makes you tick. deliberately making it really easy to find you sounds like a fast track to a surgical table near you. on the other hand, if their technical experts say "oh, he's probably just using a custom drone with a holoprojector to display digital objects" when you perform your "illusion spell", well... you're a lot less likely to get invasive experimental surgery designed to cut you open to examine various parts of your nervous system. and in my books, that's a good thing.