Well I went to my violin shop and rented a 15" viola. The guy that helped me was a violinist turned violist and he let me try out a 15" and a 16". Both could almost work with violin intervals, but the 16" instrument felt very heavy. Now the goal is to learn some Bach by June.
The Bach solo for viola would be the transcription of the six cello suites, which are mostly accessible (except the last two). He told me there is a transcription of the Bach for solo violin (which is almost accessible for the advanced violinists) for the viola. He would occasionally play those just to annoy his wife, a violin teacher.