Not meaning to rain on a parade but you can indeed change meter of a DAW session with BIAB tracks as part of the session. Its a DAW global function, not a BIAB function.
I posted a note about this...
here >
http://bb.steelguitarforum.com/viewtopic.php?t=301024
Changing pitch is probably more difficult and would be better to start over before you are all in on the session, been there done this a few times. But if you think about it, if you are using BIAB tracks, the BIAB file stays the same just make a key change and save as a new BIAB song. Then import away ! But certainly it is best to have your keys confirmed from the get go.
And, as Dom is saying and he is quite correct, using BIAB tracks and your own LIVE tracks together can produce a pretty nice session. Of course it's not to be considered a "retail" session but none the less it's pretty nice for a local home grown product. I now use BIAB exclusively for creating and building Drum tracks then moving them into Pro Tools as stereo wav files.
I've done many demo sessions for others doing the same thing. Purpose is everything. Plus no Drummer to feed. The live interaction with rhythm instruments and/or bass changes the entire dynamic of the session.
Its all good and BIAB is a great tool/resource.
I am using 2013 but have the bug to go to 2016...
Emmons L-II , Fender Telecasters, B-Benders , Eastman Mandolin ,
Pro Tools 12 on WIN 7 !
jobless- but not homeless- now retired 9 years
CURRENT MUSIC TRACKS AT >
https://tprior2241.wixsite.com/website