This combo seems crazy enough it just might work!

But my question is, can you activate the droid as your action, take the target lock, but then use the EH barrel roll (activated via EI) before doing the droid's boost? Seems like stress timing from EI would prevent that. Or droid's timing would prevent EH from occurring in the middle.

You could either A. Do the target lock then boost then EI to perform an expert barrel roll, or B. EH Barrel roll, EI to perform a targetlock then boost

This combo seems crazy enough it just might work!

But my question is, can you activate the droid as your action, take the target lock, but then use the EH barrel roll (activated via EI) before doing the droid's boost? Seems like stress timing from EI would prevent that. Or droid's timing would prevent EH from occurring in the middle.

Because R7-T1 says you may acquire a target lock, but doesn't define it as a free target lock action, you can't trigger EI from the target lock alone. It has to be an action. EI can trigger from the free boost or completing the R7-T1 action.

Or, as Torresse stated above, Take the EH action, and trigger EI (and then R7-T1) from the free barrel roll.