Sure, thicker wires is fine.
Big issue these days is that MC4 is not MC4 is not MC4. They're known for causing fires when mix-n-match.
MC4 is only UL listed when mated with select models it has been tested with. So there are several clans of MC4, each of which can work only within its own clan.
PV panel data sheets these days list the limited number of MC4 brands/models they are allowed to mate with.
Betcha there isn't even a brand/model for the MC4 integrated in the MC4 fuse holder.
If you want to do this by the book, use MC4 connectors in compliance with data sheet specs of PV panel, run the pigtail wires through glands into combiner box, and connect to screw terminals of fuse holders.
Breakers, maybe. But don't get me started on those. Previously, "polarized" breakers were sold for that purpose, hopefully labeled "+" and "-" so you connect to the correct end, except neither end was correct. Look for non-polarized breakers to have a safe installation.