Is it possible to upgrade the drive in a Time Capsule? The Time Capsule has limited space, and the price difference from 2TB to 3TB is absurd: another $200 for a single additional terabyte.  (I'm sure they'll increase that with the next round of Time Capsules, whenever they release those, but I don't know when that'll be, and I'd rather vote with my wallet to tell Apple their Time Capsule is overpriced.)

So how hard would it be to crack open a Time Capsule and upgrade the drive to something a little larger?
By all means - vote with your wallet. It's trivial for a trained technician to replace the hard drive on a Time Capsule. Rather than put the rubber covering back on the base, you can use inexpensive silicone bumpers to raise the capsule up from it's shelf. Most feel iFixit has decent repair guides if you care to DIY.