MekArcade code is very close the the Red Eclipse 1.2 base, the major addition that appear in the 0.4 release should include:
Health powerup
Armour powerup
Salvage
Destructibles
It may include the ability to carry powerups, giving an ability similar to the VTOL in Mechassault 2, indeed we may even consider a VTOL at a later date.
Mech Overheating and influence on weapons will probably be in the later half of the year as the player classes are developed further. Defensive weapons are only in the very early stages of planning and probably won't appear until probably 2013.