Plywood for an electric upright solid body?

You could do that. Plenty of EUBs are completely lacking a "body" being just a neck, nut, bridge, and tuners, most commonly with some way to attach a cymbal stand to hold it in playing position.

 

Seems fine to me. Most of the so-called hollowbody basses people buy a plywood too. Think Gibson 335. Just use decent plywood, not nasty stuff.

 

An SPF 2x8 or 2x10 would be cheaper and easier to work with.

 

Pretty sure @T_Bone_TL made that remark to reassure you that body construction is not critical.

 

I don't see why it wouldn't work. Plywood is very strong. You may need to double or triple up on your layers to get any kind of thickness though.

And I would definitely recommend going with high-end solid Baltic birch plywood, rather than the stuff you get at Home Depot or Lowe's. Home center big box birch plywood is just pine plywood with a very thin birch veneer on both faces.

 

If it will ultimately be a solid body, not a thin plywood top on a chambered body, I'd suggest using some sort of lighter-weight solid wood, rather than building up a bunch of layers of plywood. It would be lighter, and much easier to finish. Maybe basswood or alder?

 

Hammerhead is dead on about using Baltic birch. It's expensive stuff but it's void free and the veneer layers are all the same thickness so the edge will look even and pleasant instead of the often ugly layers inside run of the mill plywood. The consistent thickness of the layers also helps to balance the sheet against warpage though if you are gluing up in layers that shouldn't be a huge problem.