I forgot you mentioned the engines; I actually have a Jagermech and a Jenner sharing an XL engine because I couldn't afford to buy two lol. And I agree, when looking at engines it should state how fast the mech you will be putting it in will move, I don't know why they did it the way they did.
A single player to let you practice against AI opponents would be amazing, and like you said; just starting out and not knowing anything, and being thrown into a match against literally random players, doesn't make learning the ropes an easy thing at all. I managed to power through the learning curve and get a handle on things, but it would've been so much easier with practice against AIs, rather than just winging it and hoping for good results at the start.
The only Mechwarrior games I played other than MWO was an emulated SNES game and the Mechassault games on Xbox lol. How hard is it to find copies of some of the other games for PC? I would love to give 'em a try.