Yeah, the Delta Flyer
and the whole infinite shuttles on Voyager
(not to mention the silly need for all shuttlecraft to look like their mothership, ranging from the Chaffee
to Picard's in Insurrection
made me wonder how the actual logistics actually works)
On the runabouts, I did go back and check the transcript. You're right, it does simply say "runabout class vessels" which makes me think he meant "runabout class" as in being a size class, rather than the ship class name like people assume that dialogue to mean.
It does seem like moderately sized ships aren't super rare, but I'm also curious if they were actually as capable as they're made out to be or as small. Goroth's ship is actually decently big compared to an Archer sized escape pod
...say about ~35-50m in length and substantially beamier than a 24th century runabout, and certainly large enough to have a payload volume in the ~1500 m³ range.
The Captain's Yachts are all around that size, which means maybe they weren't rare even in Starfleet use as executive transports of one sort or another.
What seems to be the difference with something like a Danube
is that they're in a size range that's right in between those 1500 m³ range light vessels and the much smaller sub-100 m³ auxiliaries, which make them roughly analogous to advice boats, pilot boats and similar craft which were bigger than ship's boats but smaller than say a cutter or schooner. Except what's interesting is that these sub-1000m³ designs are capable of being used in ways that the previous 1500m³ designs used to fill. It's a good combination of the mother craft increasing in size and the vessels increasing in capability vs. volume.
Could you give me your thoughts on the classification scheme itself? Tried to go with as much a combination of payload types and endurance as much as anything else. Some of the classifications were required out of dialogue. For example TNG's Conspiracy
established there were still heavy cruisers and frigates.