Do you think changing the fuzzing strategy in this regard would be feasible?

yes it is feasible. but it would not be the optimal approach, for you or anyone else (unless you can convince me otherwise) :-)

here is what should work better for you:

step 1

for a new feature, run 1-x instances of afl-fuzz independent to the general fuzzing campaign. this way there is no cross pollination.

This is still not optimal because AFL++ will still at once find other supported formats and fuzz these two, making it loosing concentration on your new feature, so we want:

Focus fuzzing

when you compile for fuzzing your new feature, use selective instrumentation (AFL_LLVM_ALLOWLIST) for the functions on the path to your target functions plus your target functions themselves.

This way you only fuzz the feature that you want.

Merging to the general fuzzing campaign

once you are satisfied with fuzzing the new feature just add that corpus to the general fuzzing campaign, e.g. afl-addseeds -i focus_fuzz/main/queue -o general_fuzz

Ah, I wasn't aware of afl-addseeds, I see that's a recent addition. I think that takes the main pain points away from running a separate fuzzing campaign in paralle, so I will stick to that. Thanks for the suggestion!