Foam Feet
Think the velcro idea might work fine. All I do is carry extra foam with me for other folks - my legs are long. I put a hole in them and run a short line through them with a “washer” on the back so the cord won’t pull through and then they can be pulled out easier.
I have seen folks design “foot foam pullers” with little hook devices that can reach in and pull them out easier.
However, in the end — its just easier to tell folks to bring their own darned boat or put up with my foam setup. Your choice…
Scott
Use layers
Have it so you can remove some for taller folks, add some for shorter. Foam weighs next to noting and layers can be stored flat in a hatch if you let people demo.
Use a mix of 3", 1" and 1/2" layers depending on how much you need to foam out, adjust, etc.
FYI - Some of the The 2x2 square exercise mats are minicell - usually about 1/2" thick letting you fine tune (even just for yourself this is nice to experiment with) - with a wear resistant textured surface - and 4 packs are pretty cheap at Target and big box sport stores. Lots of different ones, some much denser and better than others.
I went back and forth on this
myself over whether an ocean cockpit would be better than a keyhole, even to the point of selling a perfectly good boat, for an older boat with an ocean. Essentially I settled with the fact that in the end, a properly outfitted keyhole is just as serviceable as an ocean, and if nothing else, ostensibly easier to get in and out of in a hurry for surf landings and takeoffs. It also makes the boat easier at resale time. The market appeal is towards keyhole.
But if I found the perfect hull and it had an ocean cockpit, it wouldn’t bother me, other than the $150 to buy a new spraydeck to fit it, and hypothetically a new $350 F#&*!ing brooks tuiliq to fit it too! 
I know beta lost to VHS, sorry beta, but it’s time to give up the ghost.