The leadership skill in 5th edition is truly badass for a player willing to play as support. Here are some of the things it can do:
1) Direct: use your leadership skill as a teamwork check for pretty much anything. one target.
2) Inspire: teamwork test bonus to surprise checks for the entire group.
3) Rally: +1 initiative for the whole group for every two hits. Extra good if one or more sammies are just 1 or 2 points short of an extra initiative pass.

4) COMMAND: TARGET ACCEPTS YOU AS THEIR COMMANDER FOR ONE ROUND PER NET HIT (contested check vs their leadership plus willpower). Ok, to be entirely fair you're looking at a bare minimum of a -8 (enemy, disastrous to npc) with up to an additional -6 easily arguable (Different social strata up to -3, Subject has superior rank [after all, he's in the command structure and the PC isn't]), throwing up to -14 in penalties on the face BEFORE the opposed check. So how does this work?

Simple. You're Joe Corpsec, and your squad is getting its ass handed to it by a bunch of cybered-up and magical terrorists. one of them yells out to drop your weapon and get out of there.
Gotta admit, it's a fairly tempting offer.

Thoughts?

Rules permit it.
Problem:
Almost no GM applies rules to social stuff, it all has to be played out somehow . .

Really? Most GMs I know adhere to the rules when rolling dice. Problem is, some won't let you roll in the first place and apply DM Fiat to all social situations. If that's the case, you either save Karma on social skills or pull a Pornomancer.

on our table, the GM leaves this choice to the players. social situation may be rolled with dice or roleplayed. 99% we roll dice first and then roleplay according to the result. We especially like doinh this with PC vs. PC interaction

1) teamwork tests often aren't that great.

2) .... if you know you need a boost to surprise checks, you're not surprised.

3) initiative boosts take place the turn after they're started or something like that, as i recall. it's a fairly obscure line of text somewhere probably in the combat chapter, and i'm short on time, so i'm not digging it up atm; i'll see about finding it later.

4) that's not leadership, that's intimidation. you're not acting as their leader, you're trying to make them afraid enough to do what you say.

The converse of this kind of sounds like a Murphy's Law thing. If you have to ask if you are surprised, you are.

while i think the command scenario given doesn't play, here's a scary thought: leadership on spirits? you are its commander by definition. extra initiative would be kickass for much the same reason it works for sams. and while a lot of spirits don't really need teamwork dice, those extra dice do potentially make a lower-force spirit more of a viable option for some tasks.

it's about planning to surprise the enemy

1) Sometimes, though, they're awesome - especially with SR5's higher skill caps and the fact that they now both raise limit and provide dice

2) When a surprise test is called for, everyone has to make one - which makes this very good for ambushes.

3) That was changed in SR5 - both positive and negative Initiative modifiers take effect immediately.

4) Whether or not its leadership, it's a rules-valid use of Leadership.

I don't think 4 works at all.

This is the base requirement for any leadership test even command.
"If you lead people who accept you as their (lone) superior, even
temporarily, you can take a Complex Action to make a
Simple Leadership + Charisma [Social] Test. How this
helps depends on what you choose to do."

So to command someone they have to accept you as their lone superior in some capacity. You can't just command people willy nilly, there needs to be some context where they see you as a superior. If you set this up with a con check first it would work, but on its own not really.