This. I've done this on a couple turbo cars that have aftermarket ECU's that are poor at controlling IAC valves. it works good once you've relearned TPS values. But with a stock ECU where you can't relearn TPS values, it could cause issues. Specifically with trans control like you said.
I'll say it usually works pretty well, but tuning can be challenging. Even turning the headlights on changes idle speed.
I disconnected the battery while i was doing the work. When I was all done and went on my 1st ride, the 1-2 shift was delayed, only the 1st time that it shifted from 1-2. After that, everything seems normal again. It seems like everything relearned what it had to learn. Only guessing that though, based on how it runs/drives.