I've installed a rear set of hydraulics for my lift and the valve I've selected actually allows for a decent amount of control over the speed the deck raises and lowers, worst case if you lower the RPMs before you move the deck it will go slower. However, the hydraulic lift isn't designed to hold the deck in place and it will leak down - you'll need to set the level control knob to keep the deck in place for more than a few minutes.
If you use the mechanical lift the deck will raise and lower the same way the 3PH arms raise and lower. This may be a better solution for some people.
I haven't had too much of an issue with the original wheels, but again I blame that on my flat property. As mentioned, the updated wheels (probably standard on new mowers) seem like they'd be a great improvement for people who have wheel gouging issues.
As for what I meant by a lower center of gravity mower, I mean pretty much anything other than a CUT retrofitted with a mower deck. Most riding mowers would fit the bill, but a ZTR is probably the better choice for a machine designed just to mow - especially if you're looking at 40 acres. They can be very fast and they probably handle slopes as well as anything could beyond some specialty mowers that can angle themselves.