Interesting. I've been doing something similar. However, instead of using b2 I just go from homing missile into 12 12 and get another couple 12s in before throwing. Admittedly, I can't remember what the damage is but execution is easy as pie. Yours is probably more optimized honestly lol. Personally, I wouldn't go as far as considering that hard to block, but it will definitely catch some people off guard and is definitely a mixup.
Good find!
One thing I've noticed is that ALL drone attacks actually (SEEM TO) take the same startup animation time. I didn't realize that before (just got back into Sonya/Special Forces). So any time you can park the drone and continue combo (11 xPark 11 for example), you could also do 11 homing missile 12 or 11 explosion (anti-air or low) 12
I know the above statement isn't specifically related to your tech, but is worth noting for other people who will come into this thread.
EDIT: Also, I just noticed I missed a bit of nuance! The b1 into EX arc kick is pretty nice. I was wondering how you completed the combo from drone b1 lol. Definitely counts as an unexpected low option.