[mEGALOMANIAC]

I thought that if there homer you didn't need to roll for reserves OR scatter... In other words you literally "point and click" and the T's arrive.

Noooo. A Teleport Homer only negates the scatter role. You still have to wait for reserves to come up. The only way to speed this up is to use plenty of IG vehicles with Improved Comms, which give you a reroll on reserves.

I imagined that on the turn that they arrive would be the same turn that the IST assaulted. It would be like this, the IST move up and call down the GK's. The GK's then shoot the Character and then the IST assault. After one turn, and the enemy at In1, then the GK's assault. As you pointed out before, this would assume perfect timing from the GK's.

You Deepstrike at the absolute beginning of the turn, before anything else. So you'd have to DS, then assault with the nearby IST, then let the GK join in the next turn.

There is 10 of them there. A character can only kill 5 at a time, tops. And again I thought that the GK's wouldn't take too long to get there.

I say again - anything that can take on a unit of GKT with a Hero can take out 10 IST like you wouldn't believe. T3 and a 4+ save don't exactly prolong a unit's life in assault. The main thing here is that you'd have to fight TWO assault MINIMUM before the GK joined it:

Your turn: GK DS, IST move in for the kill, hopefully hitting & stunning the character in the unit. Take 3-4 casualties. Take moral check, since they're very unlikely to win against a dedicated assault unit. Remember, IST aren't fearless.
Enemy's turn: Whatever else he does, which might include shooting your GK, you still have to fight another round of combat in your enemy's turn. Another 2-3 IST casualties, best case scenario. If you hit the enemy with the TH in the first round, the stun effect happens here, NOT next turn. So you have to hope to hit the character AGAIN this turn.
Your next turn: Now, assuming that the IST Vet survived two combat rounds in B2B with this uber-killer that you fear so much and still managed to hit and stun him in the enemy's turn, and the IST squad that very likely took 50% or more casualties didn't flee, and the GK squad next to you managed to not get shot up or assaulted during the enemy's turn, you can move them in and complete your plan.

The problem is that IST are too fragile for the task you're assigning them, and you're counting on the enemy to have no tricks up his sleeve and not even support this other unit in CC. Way too much coordination involved for it as well, what with bringing the GK down in a timely manner before the IST get themselves owned.