Well, you assume there is zero benefit, but you do not know that for sure. Also, if you would make sure the whole project would be open source, you would not have any maintenance issues at all, because the specific user community and source compilation would accommodate that.
Memory issues may be manageable as well, but would also require access to the source. Most of the processing of sen2cor appears to be localised, so should be streamable to a large extent. In fact, you do not have a developer community for sen2cor, exactly because it is closed at the core.
I am interested in demonstrating cheap processing solutions on RP3s (35 Euro per piece), e.g. for anyone who cannot afford big hardware solutions. That often means tailoring to low(er) bandwidth and stripping bulky processing solutions to the bare minimum. Atmospheric correction is essential for S2 use. I am looking at (open source) 6S as an alternative, because it yields comparable results to sen2cor.
I’ll check the source for the scene classification and water vapour, because I understand these are independent from the atcor part (but useful to finetune 6S).