I would say that the only ones that are really optional are the (relatively) flat, black plastic strips that cover the mounting fastener holes on the larger dinette windows
. These would be going around the perimeter of the window (in other words, these are the ones you would remove in order to get to the screws or rivets that are holding your windows
As far as the other ones go, they are there for the reasons Al mentions, i.e. to keep out water and/or dust.
Of course, except for the backframe gasket on the small windows, you could change/add most of the other ones with the windows in place, if you had to.
But if you're removing the windows, what's the rush to put them back in (maybe you are going on a camping trip?). With good heavy plastic taped on with that outdoor tape you bought, I would think you could keep the windows out for a relatively long time. Just be sure to wipe down with alcohol or etc. first so the tape is not going onto dirty fiberglass.
And really, if you needed to put the windows back in temporarily and then remove them again, it wouldn't be the end of the world. I think you'll find that once you have them in and out once, it's not that difficult (always hardest the first time). If you're not driving down the highway with the camper, then the jalousie windows
are not prone to leakage as long as you have the perimeter sealed, and perhaps that top flap gasket in place. After all, you can leave them open 24/7 without water coming in as long as you are not driving, or in a hurricane.
If it were me, I'd plan it for a time when there were no camping trips coming up, remove the windows, secure the openings in the camper, and then rebuild the windows at my leisure, inside the house, on a workbench or table. I would order the gaskets once I was able to see what was on the existing window and get the right sizes (the dinette windows are not 100% sure yet from what I can tell).
On the other hand, you could go ahead and order the parts for the small windows, since those have already been sussed out.