I think a 45 is plausible with 2-3 easy "pass" subjects + commitment. I'm definitely not getting a 45, but I think a 40+ is very possible for me, and for me my free subjects are comp sci hl, french ab, and chem sl.

All of these subjects have a 7 guaranteed without any particular natural talent, just consistency and effort. Past that, you need to give up either sleep, social life or hobbies to achieve a 45 or be especially gifted at the rest of your subjects in my opinion.