Just in case the point has been missed... If you open a FF account with each *A airline you fly and book flights crediting to each respective program you will end up with a bunch of accounts each with small mile/point balances.

You CAN credit ALL your *A travel to one *A FF program....in your case since you are G with UA that would be the best place to credit.

Not trying to insult you if you knew that...but it wasn't clear to me from your question....(better safe than sorry)