If your crossmember is rotted to hell and there is a hole in the frame (on a 2000), let me tell you... the vehicle is well on it's way to the scrapyard. It doesn't matter how nice the rest of the vehicle looks or runs.
You can put new crossmembers in, new mounts... that stuff is reasonable. Holes in frames? Speaking from someone who just went over his frame and por15'd it... mine was not even remotely close to what you describe... and it's a 1994 and I live in the great white north!
You can buy a very good condition 4x4 out of California, Arizona, Texas etc and take it home with you. You'll be paying way less than what you are indicating. You don't need to buy as new as you are saying.
You can have a blown engine and rusty body parts. The essential part is the chassis, and if you intent to own this ranger you have long term, you are nuts. Sorry to break the bad news to you...
I had a Nissan Kingcab, same problem frame rot... from the inside of the channels. Nothing you could do about it. I sold it for scrap and moved on. Not worth the money to fix, or the anxiety.
It sucks, but there no logic to spending money to fix it beyond the safety factor to get you to the point you can buy a new vehicle.
Funny, 3 years ago I replaced one of the more rearward subframe sections because parts of it were missing entirely. Then 2 years ago my buddy welded a small patch on the frame where the rear shock connects because it had a small tear. Truck has been fine since. Now sure, I doubt I'll get another 10 years out of it. But I'd be surprised if I didn't get at least another 2 years or hell, with luck maybe 4-5 more.
I guess you'd have to see it in person maybe? Here in Maine you have a yearly inspection and the truck has never failed, and they check the frame out pretty closely.