Takeoff, landing, all these things are effectively abstracted for the sake of 30m hexes & 10-second turns.
Let's be daring and look at the actual rules! :D
TW v1.2, p88: "Aerodyne DropShips, fighters, and small craft can lift off from a ground map during the Movement Phase (Ground) by accellerating down a runway or open ground until they reach liftoff velocity. The distance required for all units is twenty clear or paved hexes in a continuous line that do not change levels at any point. VSTOL-equipped units can take off in ten hexes. Players need not make a Control Roll for a horizontal liftoff."
<snarky insert - they all appear to have rough-field capacity like a Mig-23 ;) >
So simplest use of JATO/RATO is to allow a DropShip, fighter or small craft to use a 10-hex takeoff run, making a Control Roll using he VTOL Liftoff Modifiers table, and failures as per the Failed Liftoff Maneuver Table (both also on p88). TW makes no mention of thrust.
So let's dig into TO ... nope, nothing there. Can't find any minimum thrust values for TO, TM, or TW, now that I mention it.
Going back to TW, the rule is that a fighter can carry 1 bomb for every 5 tons of mass, but that each increment of 5 bombs reduces safe thrust by one. Unless you're designing 1/2 conventionals in the 5-25 ton range, I can't see - under BT dynamics - any way to model the "overloaded takeoff" aspect.
So let's just wing it, and say that JATO can either a) halve the takeoff distance, or b) allow one additional bomb to be carried. Either use requiring a Control Role using the Vertical Takeoff modifiers & failure rules. So you can take your Mosquito light fighter - 20 tons, normally 6/9, capable of carrying up to 4 bombs at 5/8 - and using JATO tack on a fifth bomb. As it happens, there's no additional thrust loss.
(A 25-ton Hurricane could use JATO to wedge on a sixth bomb, but it's clean 6/9 thrust would drop to 4/6.)
Makes sense as a home rule?