And potentially, Klingon interest preempts the PD altogether, as any natives within the Klingon sphere of interest are already acutely aware of space aliens and their death rays...
Stratos may be a Federation member world. It may be a on aligned friendly port of call. There may be political reasons why Stratos could not directly ship the needed zenite.
Well, Kirk directly states that "Ardana is a member of the Federation" - and that Plasus' Council has obligations towards "another member", that is, the planet suffering from the plague, so we can't even readily argue that Ardana would be a member but Stratos would not.
But the rest is indeed speculation. Kirk's ship may be the fastest way to deliver the aid to Merak II, either in terms of travel speed or efficacy of zenite spraying. In this case, Stratos could be well stocked in interstellar vessels, both native and visiting, but those would not enter the discussion.
It’s not clear how advanced Bajor was before the occupation. All we know is they achieved nonwarp interstellar travel 800 years ago and Cardassia knew this and covered it up because it contradicted the narrative of their superiority. We don’t know what else they covered up. All we know is that their weapons technology was behind Cardassia. They could have had warp and not made contact by choice.
Bajor is also ancient enough to have had several Warp Ages after which it may have succumbed to lower levels of technology or higher degrees of isolation. Picard speaks of an urban culture in what amounts to hundreds of thousands of years ago in "Ensign Ro"; that's ten times what it took for humans to go from earliest permanent settlements to warp.
If the push comes to a shove, "Explorers" also gives us leeway of interpretation. What nobody believes in is Bajor/Cardassia contact 800 years before the episode. But Bajor has interstellar fame going back a long time. Is that 700 years or what? Or did Bajorans travel in many directions but allegedly not to Cardassia, before deciding that traveling was for aliens? Bajorans are
extreme homebodies, never having settled their lush fifth moon and never having properly surveyed the Janitza Mountains. With such alien thinking, they could have been sitting on transwarp for millennia and considered it an utter waste of their time.
I don’t think warp travel is easier than subspace communication, just there’s no reason to invent it before warp.
Faster-than-light communications would be great for mankind right now - lightspeed holds back our computers. But warp would be great, too, with plenty of weaponizing potential even if nobody cares for the stars. It's difficult to see why a humanlike culture would always skip subspace radio until they build warp, unless there's a technological hurdle there. Then again, I just argued Bajorans are not humanlike at all...
Timo Saloniemi