Yes, but your entire base must be on the terrain piece, which with some careful positioning could be ruined with one infantry piece, because even though the lil bugger doesn't count for movement purposes, your mech can't land on him.

I think that the terrain used in the out to pasture scenario should become an official terrain.

But I think that vehicles should be slowed by it and mechs should be able to wander through it unhindered.

Also, can you use jump jets during a charge? I think you have to give a Run order, which is incompatible with JJ. If you're using jets it's by definition a DFA.

Elevated terrain was always legal. Abrupt Elevated was band from WK events.

Elevated hindering terrain is always a nice touch.

To give the broken artillery pieces that much more of an advantage.
You can't use JJ while running you have to disable them to make a run order. JJ just allows you to reach elevated terrain and to go over hindering and blocking terrain, and to make a DFA attack. Read your SE card to see about JJ.

Incorrect. Elevated terrain in not legal in head-to-head or sealed events. It is not relevant whether it is abrupt elevated or not.