The following is about answering the general question. I'd agree that it doesn't seem like it's worth it
for a Cutter.
Considering how powerful HRP / MRP are, does it make sense to pay for the improved hulls, or it's better to just Engineer the Lightweight Alloys?
Context: I'm preparing a heavily engineered Cutter for multicrew PvE, but I won't disdain using it for self-defence in PvP eventually.
Hm, well, let me compare my Gunship Coriolis build (max engineering, Reactive Surface Composite with G5 Thermal Resistant) to a build that's exactly the same except for having a Lightweight Hull with G5 Heavy Duty.
Reactive Gunship will strip the armour of Lightweight Gunship in 47 sec.
Its armour will hold for 75 sec.
...yep, it's worth it. Especially considering that 75 sec is long enough to get my shield back online to 50%, which in this case is an extra 1400-ish effective shield, adding another 13 sec onto survivability, to bring it to 47 sec Lightweight vs 88 sec Reactive.
Effective armour is 2585 vs. 2074 against absolute damage, 4494 vs 2429 against explosive, 4794 vs 2834 against kinetic, and 4794 vs 3401 against thermal.
Downsides... speed/boost goes from 240/395 to 235/387, which doesn't bother me. Jump range from 19.7 down to 18.1, not too bad on a pure combat ship but would be a problem otherwise. Handling is mostly unchanged, though roll speed drops rom 113 to 111 degrees/sec.
Of course, if money is an issue
at all, 84.4M and an extra 4M rebuy makes it not worth it.