Proxomitron is not SOCKS (it's a regular HTTP proxy with MitM capability) but it can strip HTTPS in its "half-SSL mode". Its original author is dead and it was originally designed for OpenSSL 0.9.x, but there are patches that will let it use a newer version.
I use it on my network mainly for adblocking and other page filtering, and the "HTTPS upgrade" it does is more like a side-benefit.
On the other hand, a TLS 1.2 connection coming from a client purporting to be some old version of IE on Windows tends to cause some sites to reject the request, I guess purely because of how unusual that looks.