Shortly before Origins (about which I will post shortly), I wandered over to MicroCenter and checked out their stock. Looking it over (and checking reviews online), I decided that the Samsung Galaxy Tab Pro looked like a good option. The specs are sweet -- fast processor, the current version of Android, a lovely screen, and it scarcely weighs a thing. As it turned out, MicroCenter only had the display model in-stock, but that was okay: with the floor model discount and a little haggling, I paid about $140 below list, at which point it no longer qualified as "pricey". (Which the retail price certainly is.)
Most of that discount wound up going into picking up a fancy case from Kensington. It's not technically designed for this tablet model, but turned out to fit perfectly fine, and suits my requirements nicely. The keyboard not only isn't built into the tablet, it's not actually built into the case -- it attaches to the case with a fairly strong magnet, so it is easy to bring with or not as I see fit. (Which is important, because it adds quite a bit to the weight.)
Having used this setup for a week or so now, both with the case/keyboard and not, I'm pretty happy with it. The keyboard is cramped, but no worse than my ASUS netbook's, it is nicely solid and easy to type on, it has nearly infinite battery life, and connecting it to the tablet is very easy. (And once they were paired, I basically don't have to even think about it any more: I turn on the keyboard, and *poof* it works.) The case itself fits the tablet snugly, with gaps in all the right places to access necessary ports and such; the only issue is that it doesn't have its own handle, which would have been useful. (I am pondering ways to maybe graft one on.)
The tablet works extremely well -- it feels incredibly zippy after my poor decrepit Xoom -- and the battery life is downright remarkable: I got through the entire week of Origins on less than half a charge. My only complaint is, as usual for Android, with the ways in which Samsung decided to deviate from the stock Android design, adding a bunch of largely unnecessary (but ignorable) extra "news" pages to the homescreen and gratuitously swapping the Back and Running Apps buttons.
But that is survivable, and otherwise it works *quite* nicely for my purposes. Thanks to all the commenters: while I didn't wind up going with any of the specific suggestions y'all made, the conversation did much to help me clarify my use cases, and figure out what I really needed.