Hypothetical, obviously. At the moment, boarding is basically ignored; it's just a small debuff you clear with Tactical Team and forget about, and players don't use it unless you are ridiculously keen on pet spam or similar.
BUT, lets say it has a complete revamp, using a conversion of the Commando secondary specialisation into a full specialisation. These new Commando ships are inevitably mainly going to be cruiser/carrier types, but I suppose you could also have a "strike team escort" or something, or a tachyon beam focused sci ship.
Supposing that the Commando specialisation was expanded to include space, with new kinds of Commando boff abilities that focus on things like knocking out enemy shields, or adjusting weapon damage to do more damage to shields without bleedthrough, or expands on ramming speed to allow transferring marines - things that aid the goal of being able to use the main Gather Intelligence/Innovation/Inspiration etc. mechanics that enable you to capture enemy NPC vessels.
Once captured, a vessel is treated as a bonus hangar pet until either destroyed or the end of the map, at which point it becomes a pile of Dil, EC, R&D materials or marks, or... whatever suits balancing. Based on it's ranking, so capturing a Dreadnought is worth a lot more than capturing an escort.
Obviously, it won't be a meta specialisation - it takes time to capture a vessel after all, estimating at least a minute, by which time a lot of stuff has been blown up. But, it could be an interesting new playstyle, and one with plenty of onscreen evidence to back it up.
Some basic ideas:
Galaxy class Commando Cruiser - as documented in Yesterday's Enterprise TNG 3x15, while it isn't Starfleet's main role for the ship, the Galaxy class is able to carry 6000 marines. As well as that, being an Exploration Cruiser with large numbers of research labs and sensor thingys well employed throughout TNGs run for all kinds of weird and wonderful tasks makes the Galaxy class a good candidate for Commando conversion. Further, let's face it, the Galaxy class is pretty badly done by in STO, and this is an opportunity to give it a new specialisation that really makes the old ship shine. Failing that, some sort of fancy tricks with a deflector and secondary deflector is a very Starfleet thing to do.
Let's face it, ramming your enemy and then jumping onto their ship with your Bat'leth in hand is the Klingon way. What Klingon ship wouldn't work for boarding? It's a defining tactic from TOS onwards, shown using... well, everything from shuttles upwards. Instinct says either a Bird of Prey as a strike team raider, or something like a Vo'devwl variant for ramming.
Not many on screen options here, as far as I can remember anyway. Perhaps a Reman avenue to explore? First Contact mentions Remans being used as shock troops in the Dominion War. I think a Reman Commando science ship could be an intriguing option to explore. Alternatively, drawing on the Suliban links already established could have a swarm of cell ship boarding parties.
Again, the nature of Jem'Hadar means they have a lot of options here, with the Jem'Hadar Battle Cruiser fitting in straight from the Dominion War. Personally, I think a sci ship suits them the least.