Dear @fnordlyone I'm a bit hesitant to make a suggestion to fix the hole. I'm not sure what will happen to the foam adjacent to it. If the repair is on the stiff side, it could cause further cracking. If the adhesive does not like the original foam, especially in its deteriorated state, it might dissolve it. Perhaps Mr. @beans-on-toast or The @agedhorse would have some suggestions.
Just thinking out loud here, not a solid suggestion without adult commentary: I noticed they do have new foam for Yamaha 10's, two kits, depending on cone diameter:
Yamaha Speaker Repair Foam Edge Kits Their method of refoaming involves leaving the cone in place and going by feel to center the cone. It's pretty easy, works for my home stereo speakers, but Andy has warned me that this is not a good method for Pro Audi/MI speakers. IDK if these could be an exception. IDK if you could get away with skipping their method and keep 2/3 of the old foam on while gluing the new surround. That might be tough to do and get the new nice and neat. Maybe a patch can be made from the kit? My shipment from them actually came packed in scrap speaker foams and cloths. Maybe call them and see if they think their adhesive and sealer will work well for these and see if they can use some scrap black to pack your order.
Believe it or not, the first time I "refoamed" my Marantz speakers (4 10's, all for shot and rubbing), I couldn't come up with $100 for proper surrounds. Just out of the Navy, employed making little money, forced unannounced and unpaid vacation, sold my refrigerator to buy food. So I used pantyhose and elmers rubber cement. I stretched the first way too tight, the other three came out great. I left that one too tight and played them for ten years before I decided I would get the parts and do a nicer job. That rubber cement was a real PITA to get off the paper cones! Those lasted another 10 years, then I got the simply speakers kit and did it their way. The only difference was the "tight" one had no deep bass. You probably don't want to go that route! You might wonder why I even admit to doing this. Well, if nothing else and you are willing to roll the dice, you might get by with holding your head up high, going into a store you will probably never want to return to, and buy some nice black hose. Then glue it on with rubber cement and coat it to seal. Test the cement first to see if it dissolves the foam. A small amount of rubber cement on the cone might not be too bad to get off later. All around on 4 tens cost me a couple evenings, then the actual refoam was done in one evening.
IMO best bet is to take it to a pro shop for refoaming. Even if it costs as much as a used replacement, you know these are low mileage and the only thing wrong is the foam deteriorated.
Don't listen to me, I'm a hack!