I think having the user type answers is a huge problem. An SRS where you grade yourself (Mnemosyne, for example) allows for fuzzy answers and typos. Your system

I think having the user type answers is a huge problem. An SRS where you grade yourself (Mnemosyne, for example) allows for fuzzy answers and typos. Your system apparently does not. There are also SRSes which allow for audio and video in questions and answers. Clearly that is impossible to automatically check.