Well, supposedly they're rated for up to 81 mph, so I'm not sure you need to limp anywhere. Granted, I wouldn't be too aggressive on acceleration and braking as they'd likely do burn outs, but you can drive at decent speeds until you get to a shop to patch/replace the tire.
A full size spare is also twice as thick as the modern spare, so it uses up that much more room. Room, most would likely rather not have to give up over a compact spare.
Comfort and driving wise I would want to have a full size spare. But having a full size spare actually requires you to rotate them in when you rotate tires to keep the wear even, otherwise you have one tire that is practically brand new that is mismatched from the other three. And that is generally not a good thing when driving.
So you might say its fine to drive mismatched tires only temporarily... Well, then might as well get a compact spare and save some room/weight/etc.
While you do need to cut through the liner if you want to use attachment points to secure the tire, I don't think there's anything that needs to be cut. The "bar" that separates the shallow and deep under trunk is bolted on (two at each end). In fact, its those mounting spots that is used for the strap.
What I tend to try to do is, if I need to modify anything, that can't be returned to how it was from factory (ie, cut something up), I would see if I can buy a replacement and modify that instead. So, maybe look for a cheaper replacement carpet liner and cut that.
