Hi W.mass,
great question to put out there. in two out of three of my last builds i went with foam bulkheads...so happy to share what i learned/how they are doing.
first, for the two boats i went with foam, i was very focused on building light. one was a 29 lb petrel play for myself and the other was a 25 lb frej for my wife (pictures below)

so my thoughts in no particular order:
if you want to build the lightest boat possible, every bit counts and a set of adjustable footbraces, the bolts and the glass will set you back about 1 lb (16 oz) which is a lot. foam, and by foam i mean, mini-cell foam, will only set you back about 3 oz. so if you are trying to keep it light consider foam.
foam to me does not mean it's not adjustable....it just means its not adjustable when underway and requires a bit of planning. i use minicell foam for my "foam footpegs" and they are cut in such a way(slightly oversized) such that i wedge them into the hull and against the bulkhead. i carry some additional 'slices' in my forward compartment so that i can adjust for different foot lengths by adding or taking away slices.
i have found no need to add more glass into the bulkhead than normal bulkhead construction. they are plenty strong and you would be pushing them into the narrower part of the boat so you would have to break the bulkhead or the hull to move them forward. also, the load with foam is spread pretty widely compared to the two bolts that hold a traditional track or a footbrace mounting kit....which should typically be reinforced around the holes/mounting kit with extra glass to spread the load.
the cool thing about foam is that cosemtically, they do not require holes in the hull and they are easy to re-do if you want to keep adapting them.
the downside, if you want to call it that, is that if you want 'no give' in terms of your foot pressure and the feedback it gives you, foam, becuase it has some flex, will give you a bit of spongy feel. so far this has not been a problem....but it does feel a different if you push hard. also, of course, if you are used to having a lot of different people use your boat and doing this on the fly (e.g., do you want to take my boat out for a spin?), i would probably want the foot pegs.
the only other thing i will share is for both boats with foam, i did pre-drill (and then filled them) the holes for regular tracks in case i ever wanted to cut it over to the other system. since the hulls were both dark, you can't see that i did that unless you look really carefully. but so far, no urge to make the change.
below is a picture from the cockpit of my 'foam foot-peg' on the petrel. in this case, the forward bulkhead is also foam (3 inch thick minicell glued in with 5200 adhesive). on my frej, the forward bulkhead happens to be wood. so far, this system had worked well and proven very strong and light and i have been able to craft the boat to adjust to the few people i allow to use them.

happy to answer any other questions.
h