I don't think that KSA will participate. Personally I would not want to see it. Those militaries will be under Israeli and US control and do their bidding most likely. De facto another potential occupation force. It will only create unnecessary rifts.
There is also the potential of pro-Iranian regime groups within Gaza attacking KSA soldiers or doing false flag operations in order to defame KSA. Like they are doing 24/7 already in the media anyway. Similarly it would not take much for pro-Israel Gaza militias to be told by Israel to attack KSA/Muslim soldiers and this way create a rift. Some of the first things that they would try to do most likely in order to create a rift between Muslim and Arab peoples.
Let those who destroyed Gaza (Israel, US and West) do the rebuilding and whatever they have agreed to after this so-called "peace deal".
Don't involve people/nations that have nothing to do with it only to later blame them/us if things go wrong.
Anyway let Egypt, Jordan, Qatar and Turkey do it if they insist. They are the ones involved with this "peace deal" and all of those negotiations that so far have amounted to nothing in terms of long-term solutions for this conflict.
Simply put this "peace deal" is a US/Israeli creation and serves their interests.
Only exception would be if a combined Palestinian political agreement is reached and they agree to the plan and if US/Israel can guarantee that they will not try to create rifts/break the deal. Only then would I support it begrudgingly.
This whole thing should be studied carefully and guarantees (in public and written) should be given beforehand regardless of which Muslim militaries will be involved if any.
BTW Israel has broken their own so-called peace deal numerous times and killed almost 200 Palestinians. Zero consequences for that behavior. The genocide not continuing as before is not a "victory" by itself as it should never have happened to begin with and the key is a long-term solution to this conflict and ultimately Palestinian statehood which this peace deal has done nothing about.