I don't have first hand experience of this, but I have read several things suggesting that a big part of the problem with OpenSSL is the API - that it doesn't h

I don't have first hand experience of this, but I have read several things suggesting that a big part of the problem with OpenSSL is the API - that it doesn't help you to make sensible security decisions. A large part of the design of RusTLS seems to be to have sensible defaults and to not make available insecure algorithms. That said, we shouldn't let perfect be the enemy of good. An OpenSSL compatible implementation with no memory issues would definitely be good.