so, i wanna look at the pad contact area on the disc to see that there's at least enough space for the pad to mate-up with the rotor nice?
then what about rotor thickness?
are there any generic rules-of-thumb for caliper / rotor compatibility?
What rotors seem to work for Hope M4s?
My rule of thumb is that swapping around rotors is never a good idea.
Best case, you'll get acceptable results. Worst case, it won't work right at all.
the brake tracks on rotors are designed to work with specific pads. you'd need to find rotors of the same thickness and brake track width. you can get close, but it'll never be perfect.
If you have the cash to buy Hope brakes, you can spend a little bit more and get the proper rotors.
do a search. a lot of people disagree with me. maybe your standard for "acceptable performance" is lower than mine.