If a trade is accepted before the Playoff roster deadline but processed AFTER the playoff roster deadline - will that player be eligible for my playoff roster?

I'm about 95% sure the answer is, "no." He won't have been on your 40-man by the playoff roster deadline. Anyone else feel more certain?

This is something they need to fix. The same is with the transaction deadline. I think it needs to be that when a trade is accepted before the transaction deadline OR the playoff roster deadline, they need to go through by the date they were accepted, not when it was completed.

I believe, the trades cannot be completed until at least 17 people vote on them. You should not be penalized because people wait forever to check in or to accept the trades.

Trades complete 24 hours, then the next half-cycle, after they are accepted. Regardless of how many votes they have.