As far as I understood the trick when using JJ on the move is to cut speed in midair and gentle bring it back when coming into the landing sequence, so you have a rolling start of some sort...i only happened to pull this off twice in 2xPPC Osiris, where I jumped, shot my PPCs over a ridge, cut speed to zero by accident and then in hectic put it back to a third or so...gave me a nice roll-in from landing to 30 kp/h.
Sure, its not what many of us are used to (MW4 soft-landing feature) but the fact remains that catapulting 30+ metric tons of non-aerodynamically formed metal are going to have some impact (try to calculate the landing force for 2-feeted machines dropping from more than 30 meters height and having a touching zone of lets say 2squaremeters for both feet accumulated^^) when they touch ground again(think of the jolt any vehicle is suffering when getting airborne and touching ground again...forward momentum will be still there, but some will dissipate into the frame, the suspension and into anything that makes up the vehicle).
The heat spike from jumping is quite tolerable reminding the fact that you have an ability at hand that other assets lack and when properly used will ensure your victory through being able to scout-hop over ridges, poptart on the move and get to places where other assets couldnt even dream of.
And for MASC heat: acceptable as is, because: the mymomers driving your mech need a massive overdosing of energy to quicken their movement and therefore the heat should if not must build up from draining more energy from the reactor and therefore generating more heat while still being able to sufficiently power the rest of the mech as well(there is a nucular reaction in there----> more demand, more reaction, more heat ).
Just my 2 cents

<3 to the devs