Ftb ql and Canon AE 1 program. You can used Minolta, Pentax and other lenses with the Canons and there's loads of good Canon Glass out there in FL and FD and, with other brands in general, M42 thread mount.
I had professionally very good experiences with the Pentax LX, so, as the MX is the smaler brother of the LX, I would chose the MX hoping it would be at least as good as the LX.
But, I have to confess, I gave up with 35mm film...
I would go for the OM4Ti and none of the others. Actually, I have one of these.
second choice would be all of the Minoltas.
You really don't need to start collection lenses for multiple mounts.
Is that an MX like everybody says, or an ME like the OP said in post #1? I like the MX, dislike the ME.
I would have loved an FTb in 1973, but couldn't afford it. I could afford a Yashica TL Electro-X. The 50 was a good lens (still use it!) and the body lasted 9 years as my only camera.