I didn't think of pump jacks but that could work if the floor will support the 4x4 and you can support the top. The top brace has to be secured to something, normally the roof. I used them years ago when I resided 3 sides of our two story house. I was doing it nights and weekends so it was cheaper just to buy them than to rent. I also like not having to worry about getting tools back or getting charged more. So whenever the cost to own or rent are close, I own. Provided I have a place to store.
You don't need aluminum walk boards with the narrow scaffold I would use, the walk board is an integral part of that system - the metal frame both braces the scaffold and provides your work surface. Mine has 1/2 plywood over 3/4 steel angle iron. It is plenty sturdy for 1 person. I would check before getting two guys on it - and it wouldn't be enough space for two people to work comfortably. It has wheels so if you had a person on the ground cutting and handing boards up, they could reposition you. I wouldn't want to be on the scaffold while they did it, however. I use a step ladder to get on and off, I also didn't trust it to stay put while I climbed it. Full size scaffold is so much bigger and heavier I had no issue with climbing on it. If I couldn't reach side to side of the space you want to cover, I would probably make sure I could nail to two or three studs in the center from one location of the scaffold. If so, you could easily get all the boards up from one spot and go back and do the ends from repositioned scaffold or a ladder. Moving the scaffold platform on the narrow scaffold is neither real hard or real easy, however. You have to get off but you can do a corner at a time. Four sets so you could cover the entire area and just reposition down as you get board installed would work better. That would also allow two people to be up with one cutting. and probably both nailing (pass a nailer or have two).