Now that would be a problem. The turntable is
no bigger than the TOS shuttle, meaning that any craft of increased size of crew cabin or increased length of warp nacelles would be confined to the upper deck. That's bound to limit attempts to increase endurance or speed.
Then again, there isn't necessarily a need to stow runabout-type craft aboard starships. Indeed, that could be the defining factor: if it fits into a starship in the operational sense, it's a shuttlecraft - if not, it's a runabout. (More like "if it serves as a starship's means of pendulum transit, it's a shuttlecraft - if not, it's a runabout", but that's essentially the same thing in other words.)
The
Copernicus seemed luxurious enough, with a table and stools erected mid-cabin, and no doubt with further comforts like bunks stowed in the walls, perhaps also with internal partitions that can be collapsed into the walls.
Indeed, we could say that the internal multi-section partition wall or curtain we see
here and the doors we see
here are the same thing, just an
internal partition - and the actual vacuum-holding thing at the stern of the craft is the entire sloping wedge section that we witness in the
exterior view, neatly hinging down to form a ladderway to the surface (otherwise where does the stern section go, and how do our heroes get down?).
And we see this craft in interstellar transit all right - they are said to be "passing" an entire star system. All the
Copernicus lacks, then, is a shipboard transporter (probably not available back then) and clear evidence of armament (but I could easily accept something comparable to the
Danube guns in terms of relative firepower).
Timo Saloniemi