Thanks everybody for the comments!

I've just adjusted the velocity of the piano from 2:50 to 2:56 wich, in fact, was too loud.

Regarding the process, I started figuring out the chords of the original song on BIAB with ACW, wich is a great tool to make the process much faster. Then I tried different tempos, styles, and individual tracks until I founded something I liked (wich is, in my opinion one of the strongests points of BIAB) and changed the structure to my taste. The "creative" process (in wich BIAB has definitely a central role) finished here; then I exported all tracks to REAPER, where I re-recorded the bass (using a Fender American Jazz Bass, I mean THE BASS), the piano (using NI New York Grand), some percussion tracks (I left congas and drums from the orignal BIAB arrangment) and the vocals. I wanted the mix as natural as possible, so the only effects I applied were compression (bass and vocals) and reverb (vocals, percussion group and piano), using the internal effects of REAPER. Finally, there is a limiter on the master track.

Thanks again for your time.