Yeah alright maybe that's a bit ambitious, even if I brought my stand and a tarp. Still, I'd like to do a side-by-side somehow. Maybe just ride the same trail on back-to-back days with different forks.Trailside fork swaps? Nah, you're not gonna do that. Talk about a pain in the ass. Go ahead and try it once to see what I'm talking about. You'll need a 2nd crown race for your extra fork. You'll have to be extra careful you don't drop headset parts in the dirt. You'll need a work stand. You'll have to be really finicky about aligning the front brake caliper when you swap it over. You'll have to make sure the steerer tubes are cut the exact same length before you even start, so you don't have to worry about different spacer stacks.
Also, I wouldn't recommend just buying 2 of whatever of the same thing for the two of you. There's really no good reason to do that.
We both got the same XC bike because I used to get a discount from the shop that sponsored my road team, and they were a Scott dealer. These days, marriage-wise . . . if I went and spent $3k on a full sus bike and she was still on the old hardtail . . . will probably have to both upgrade bikes at the same time. The question is what each of us upgrade to. By the time we're ready to drop $$ on trail bikes, we'd probably get different things, especially if we're buying used.