It's the no warp thing that really limits its ability. The saucer can 1. limp back home. or 2. stay put while the rest of the ship does something risky and then hope they don't have to resort to number 1.
I could see the saucer section being left in orbit to assist with evacuations while the stardrive section "goes for help" but even this seems like a bit situational.
You are correct. We can't really infer much about Una's citizenship status and so letters of recommendation or sponsorships aren't of concern. But with that being said - if Una can be a citizen and be modified then so could Dal. Albeit the restriction on genetically modified people serving in Starfleet seems to stick all the way through to the late 2370s and early 2380s at least.
In fact, unfortunately, we still see a fair amount of bigotry towards modified people persisting into the 2370s, but perhaps by then the difference between a modified Ilyrian and a modified human are more substantial. Dal, being a non-human (I guess?) might face less bigotry in his era than Una faced in hers.