I know it`s hard to do, but:
* Kicks with Real instruments
Serveral Kick situations (shots, holds, etc), so you can have some accents / shots with the real instruments.
Also a simple hold function, where the chord is held over at least one bar would be nice.
Especially for endings, I wish that the Real drums were able to do the usual rolls over the cymbals and toms at the end.
* A Drums Solo
I know one can work around this by pasting the trade 4 (4 bar solso) at one another in Real Band, but thats quite some effort and hard to do in BB.
* Multiple VSTi support