Really interesting thread!
Once specific idea I've been kicking around is "Escort Package" giving significant speed/maneuverability and range bonuses when near a larger ship (actual details super TBD). And perhaps "Assault Package" giving some tanking or damage bonuses, hmm.
But yeah, for speed, the idea would be that they can rotate in and out of combat more easily when near a larger ship, but can't actually act as a "super frigate" because the speed is tied to proximity to a larger ship. Not entirely sure how well this would work out in practice/how well the AI might handle this, though, hmm.
If you can't make it work with the AI, I have some alternatives for the assault and escort package that allow it to fill the desired roles, but don't require it to be within a certain range of a friendly larger ship.
Escort package: For a reduction in both speed and flux dissipation, the ship gets a combination of the following, i.e. whatever you think is fair.
Higher efficiency shields, more armor and hull, higher active venting rate, and ignores flares.
EP should be all about making the ship tankier so it can stand alongside the ship it is escorting.
Assault package: For the removal of active venting, the ship permanently gains the 0 flux bonus to speed.
That's it, one of the problems with destroyers is they can't back off in time. SO currently fixes this issue, so AP would just be SO without the PPT malus, increase in speed, and flux dissipation boost.
Less interesting but is needed as one of the major reasons SO is used is for its 0 flux boost.
This is a really interesting idea. A lot of the things mentioned in this thread address how destroyers are inhabiting a somewhat awkward middle ground between frigates and cruisers, but if the individual ships get changed one way or the other, it cuts down on build diversity. Here, destroyers at least maintain a couple different options for if they want to inhabit a more line-battle doctrine, or aim for speed and pulling the enemy fleet apart. I think a range buff for the Escort Package would be important though; part of why destroyers die so often is that they have such a range malus compared to their cruiser brethren. That 20% from ITU makes a big difference in survivability on its own!
Would these hullmods be destroyer-only though? If they are available to cruisers, capitals, and/or frigates, one could see how the destroyer would still be left behind by other size classes speccing into their respective strengths. I don't think destroyer-only hullmods would be
entirely without precedent. After all, we have DTC (specific to cruiser/capital), Converted Hangar (specific to non-frigate), SO (specific to non-capital), etc. But the general pattern is that hullmods can be fit on a ship any size X or above/below. There is no precedent for a hullmod that can only be fit to a specific size, and not to those above
nor below. Which is one of the reasons why I think Alex considers different buffs for different sizes, so each size can get its own bonus (that may be more or less useful than the other sizes) without restricting the hullmod to a middle size alone.
I just think that, if the bonuses for frigates/cruisers/capitals are good enough, the destroyer still has an awkward place, and if the bonuses are bad enough, why offer the hullmod for other sizes at all? Or maybe the bonuses are more qualitative differences (ie, not just range/speed/health buffs), which could be really interesting, but could also make for one heckin' wacky tooltip! For example, imagine if there was an Escort Package effect where destroyers could split the flux damage they and/or their escort target take between the two ships (or split more ways, with more escorts). That effect is obviously pretty wacky, sounds like a mod effect, and could have some majorly unintended consequences, but by hell would it shake things up and offer some build considerations! Or even something as simple as, "escorting ships gain the officer skills of the ship they escort", however that might be done. And then maybe each size class gets their own bonus, depending on the intended role of the hullmod/ship size.
All this to say, I'd rather have either a destroyer-only hullmod or a hullmod that makes drastic and qualitative changes to gameplay over a new hullmod that ends up granting quantitative effects to all the sizes and still leaving destroyers behind.