The one IMTU is a modernized version of the old High Frontier Consortium Lightnings.
It can handle Jump-3 with the "enhanced fuel" manufactured at a given place(that is a local Macguffin, and has to do with the plot). It also carries two wing-shaped external cradles which often carry drop-tanks.
As I am not experienced at construction of starships, I really do not wish for overly harsh criticism of this arrangement, by the way.
Most of the Staterooms were taken out. There is a galley next to the bridge which serves as a social center, and also doubles as a sort of sub-bridge command center for the second mate, though it really doesn't have the communications for that(as it is right next to the bridge, yelling is often good enough).
Anyway, the Lightning was chosen as a model mainly because it is a utility ship shifting from long-range trade to naval auxiliary and back according to need. This suits my tale which is sort of a "space cossacks" type plot. The chief disadvantage is lack of cargo space which precludes using low price cargo very often.
What I would find interesting, is an example of some modernizations which would work in the Emperor Strephon time. I would also find suggestions for cosmetic or functional customizations interesting, though as to the former I have my own ideas.