Thank you for answering my worries. This post would be better if I dig more into Symbolics.jl, but as I explained what my pet project needs now is SymbolicUtils.jl, so I will be messing around (hopeful not literally 
) in that part of ecosystem.
Also @carette is posting now his reflections on Zulip, which are streatching to maximum my \lambda calculus and algebra knowledge, so you have true CAS expertise to evaluate your project choices.
Sound very exiting. I wish you luck.