Can it take a good beating? I'm unaware of anything that can take MORE of a beating than a VXL Stampede.
Hop-Ups: Only things it really needs out of the box would be aluminum shock caps (or big-bore aluminum shocks) if you want to do a lot of jumping.
And a wide front bumper: RPM Bumper
The wheelie bar is included with the VXL Stampede.
Steel upgrades to chassis, tranny, are already done. Beefy bearings and carriers already upgraded. It's ready to go.
Additionl metal hop-ups? Well, if you want to get fancy, lots of aluminum available from FASTLANEMACHINES.COM but the most useful thing they sell is the all aluminum transmission case. It's nice because it acts like one huge heat-sink to keep that VXL motor nice and cool.
As for Lipos... well, yes. The BIGGER the better. MaxAmps.com seems to be the popular choice. For one thing, you can order them directly with the new Traxxas high-current connector already installed. You'll want both 2S and 3S packs. The 5000 packs seem to be the easiest fit. The 3S 5000 pack, the battery cover won't close so you have to use velcro straps to secure the battery in the tray.
You asked "Can it only hold up to 3S"... well, it's only RATED for 3S. Don't know if the ESC will take more than that. I know that with the Mamba Max controller, you CAN run 4S, if you disable the built-in BEC and install a seperate one. Voids your warranty of course, but then again, if you're after that kind of speed, money shouldn't be an issue.
However, you're already pushing 65mph on 3S. How fast do you think you want to go in a little 10th scale plastic car? You might want to see how it performs on 3S before considering anything more.
For instance, on 3S with the "race" pinion installed (which is included), if you can hold full throttle for 3 seconds, it will be so far away you'll need a pair of binoculars to SEE it. And don't forget the stopping distance you'll need. Best I can manage is about 2 seconds of full throttle, and at that, the stopping distance is a problem for me. I run out of road.
Then again, my VXL is the Rustler, which is about 5mph faster than the Stampede.
Oh yes. I think you'll be pleased with the VXL.