When SFTP and FTPS were introduced into Total Commander a long time ago, this was the time to make sure / find a way that both looked for the partially identical DLLs in the same folder(s).
To be fair to author, SSL support for internal FTP was added sooner than SFTP plugin was created (at that point SFTP was just a distant dream, because there wasn't any library for it and author himself couldn't do much with cryptography because of local laws, as I understood it). And %COMMANDER_PATH% as location for dlls was obvious choice, because system looks for them in executable's directory by default. I don't think any of us would do it differently at that time. So the first step towards current problems was taken.
... and one (SFTP) expected to find them in its plugin folder.
Or also in %COMMANDER_PATH%, or better, in any standard search path. And internal FTPS did initially the same, but was later changed to not look into directories in PATH in the name of security (*1).
So far there was no problem. It came with TC64 and support for having it together with TC32 in the same directory. Which in theory is completely unnecessary, because as user you care only about shared settings. And I don't see why it wouldn't be possible even with separate directories. But - and that's the major problem - it would not just magically work, without user touching anything. And so here comes our friend, the backward compatibility. Don't get me wrong, I love it, but sometimes... ;)
One approach might be by introducing yet another 4 initialization parameters...
I'd rather stay with standard way how system searches for dlls. So I'd remove (*1), which would solve it for people who want to manage their PATHs, lets call them advanced users who know what they're doing and don't need TC to protect them.
And then, as the convenience for others, have e.g. %COMMANDER_PATH%\lib32 and %COMMANDER_PATH%\lib64 and automatically add them at the beginning of search path for whole TC process (lib32 for TC32 and lib64 for TC64). That way anything in there would be available to TC and any plugin. And it would of course be the recommended locations for dlls and therefore safe, because they would be first loaded from there and potentically malicious dlls somewhere in PATH would not be touched.