Neat concept. I like the idea of using non-Cap "WarShips" as FTL assault DropShips.
Incidentally, the reduction in tonnage should "theoretically" ease production of these ships. Though I hear sub-compact and compact JumpShip cores tend to be more difficult to construct. (I use the time piece theory. Smaller = More difficult.)
(Insert Sarcasm for entire line.)
As for WarShips in general, IMO I just feel like the reduction is all part of the game/fiction cycle. With BattleTech's resurgence in popularity and the fact that at its core the game is about big stompy robots, it is inevitable that "support" units like tanks, fighters, etc., would wax and wane with the storyline.
Mark my words, next round of universe changing events, say the Jihad or Clan Invasion Mk. II will see new WarShips or new "support" units to enrich the pre-existing game. Also, keep in mind that BattleTech is rich in eras where WarShips were common and plentiful. That's what I'm loving about the Historical series. They allow CGL to provide us with new WarShips and other goodies without having to impact the current evolving storyline.
But I do like the idea of hammering it out in space for more than two-three turns using standard weapons. Getting hit by two Hvy NGauss rounds, or a couple of Krakens is just brutal against anything short of a Texas.