Viewed in a certain light, it is almost comical (and at the risk of not putting enough thought into it):

The US Army uses the word "deployability", in roughly the same way a panic-stricken student says that he/she needs to "study" the night before a big exam. Plenty of talk, and disjointed, but all too brief, spurts of action.

The C-17 is outstanding, and the Stryker (and Stryker brigade design) is decent, good even - heck, excellent considering the alternative was previously foot-mobile infantry with some Up-armored Humvees.

So I'm a little surprised that we don't have more airlift, or a replacement for the Herc (SFC W is right, the C-130 can land in an amazingly short distance, on an aircraft carrier even, but the interior dimensions are a bit cramped for serious vehicles). I sat next to a C-17 maintenance officer (either commissioned or NCO - I didn't pry) on a flight one time - he talked about how rapidly those airframes are being worn out - and we really don't have that many.

Most of all, our rapid deployment forces (light infantry and SOF) too often seem to eschew armor to the point of a fetish. Which isn't helped by a few military "experts" both in and out of uniform, who have a seemingly endless stream of excuses for why armor isn't useful or applicable... and who in at least one case managed to be shocked (shocked!) that having a few tanks around in an urban fight, or even in A-stan (a la a company of Canadian Leopards) turns out to be a good idea.

And yet, (after the Sheridan) there was never a US counterpart to the BMD or Wiesel, the more compact French armored cars, or even the Scorpion /Scimitar. Seriously?

Were we serious, we would have come up with something (and actually deployed it). No good reason not to give early-entry commanders another tool in the bag of tricks.
That said, I think that the idea of a QRF company of tanks and Brads isn't as bad a fit as it might first appear.
The M1, with a few improvements (more fuel efficient engine, for example - not too hard to do) could make it less difficult to support - and thus more useful in an austere environment. Usually, we either seem to have the time, or make the time, to get some heavy armor into theater anyway. ...and an M1 can give you a very nice... edge.

We could modify just a battalion, for example. That might be one good mission set for an elite armor unit. Modify vehicles to use less fuel, perhaps add more mechanics and much, much more PLL...
If you can only send one company, one battalion, or one brigade/regiment of armor, then it may as well be a great one.

Besides, from what I've heard, a fair number of tankers have been in Humvees, and not their tanks, for a long, long time. It wouldn't hurt to have armored units that were not subjected to that abuse, and thus ready to go for anything unforeseen. (I always find it suspect, that for a long time it was said that "we always are preparing for the last war", and I haven't heard it in a while; now I hear that insurgencies are the only way wars will ever be fought in the future. Ever. Hmmm... noticeably we still needed to kick down the door in '03...)

A second possibility could be armored units specially trained and equipped to support infantry units in urban combat - since that is also (theoretically) the wave of the future. I'm not entirely sure what that should look like, although the Russians have some ideas about it, and it seems to include some vehicles with multiple auto-cannons and heavy armor.

We also seem to lead with our Cav organizations (both Gulf Wars) and they ended up doing a good bit of fighting. Heh, historically, armored scouts always end up fighting, no matter how often some say they shouldn't.
While the 3rd ACR still has that punch (41/41 Tanks/Brads per squadron, with all 3 Armored Cav Squadrons, the Heavy ACR has twice as many of each vehicle as a Heavy BCT, and it has an Air Cav Squadron, and the other support...), the DivCav Squadrons that were so excellent, have now been dismantled, and the HBCT Cav Squadron certainly couldn't mix it up the way the DivCav could (in spite of the fact that the Heavy BCT's desperately need more combat power). Quite ironic that we nearly dismantled all of the Cav organizations, in the name of "modularity".

This could be a third possible mission set for "special" armor units - the Armored Cav mission (the traditional guard, cover, screen, along with raids), only this time they get some extra resources and other ups. While I was in the 3rd ACR, I saw us get more ammo and training time than my friends in regular units (admittedly not a very scientific study), but I don't think that was institutionalized (I recall that the official ammo allocations were the same as a regular mech or armor battalion, adjusting for the number of vehicles) - so I am just hopelessly biased...