I like this thread... well researched with a lot of actual information and effort spent. So take these comments in the spirit of trying to add to the discussion not criticize.
The Face Turn - Big stated he wanted to rap more conscious topics and he was moving on from the mafioso/versace subject matter he was more known for. This would have been the biggest heel/face turn in history of rap. I dont think he woulda gone conscious like say KRS-1 or Rakim, I think he was more going for a Slick Rick, meaning witty story telling with a theme behind it. I think 'Sky's The Limit'/'Juicy' is basically the mold of song that biggie might have been aiming for... Also with this angle I really don't know if Puffy would have let this go down. That was a major change to the direction of his cash cow... Its funny to think about it all we got a chance to hear from biggie was... its as if nas had died after it was written, or jigga had died after reasonable doubt... we really dont know what his legacy would have been. his whole legacy might be completely different today
The Triple CD - Would have never gone down... this has never been successfully pulled off by a big name rap artist. It was a concept that was floated around a lot at that time, but i dont think any of the big names who talked about this actually made it to a release.
The Fall Off - Almost undeniable... i mean in the history of rap there are probably the only artist who can be considered to never have truly fallen off is Eminem and Jigga... and both have often been sited as having a huge decrease in passion/effort/final product... so just based off statistics we have to assume biggie woulda fallen off eventually... my personal perspective is hip hop was already turning on big time right before his death, so i think it woulda been earlier rather later