A lot of the campaign stories I love have situations where a new size class of ship is built, and it can't be deployed outside the solar system or jump network because there is no jump ship big enough for it yet.
So why not have the starting ship designs built with commercial engines, size 25+ engines with 50% reduced power? Build them about 60% engine or so, and they will be as fast as conventional ships with 30% engine, with cheap efficient engines.
Maybe a meson tech fleet too, which goes for a robust engines as armor philosophy, since they can't shield or armor against mesons, they build systems that can take a few hits.
They could then not need military jump engines developed until they were contemplating jump assaults, and conventional start empires aren't going to be contemplating jump assaults early. If they are assaulting another system early, the other guys probably haven't developed jump theory yet.
The smallest effective design they could make would be about 1,700 - 2,000 tons, 1 size 25 engine with 9-15 HS left over (not including armor, crew, maintenance). They would probably have multiple size 25 engines on the smaller designs, to allow for some mobility if an engine was hit. They would need to build larger shipyards for the same ship payload, and being larger, they would be more vulnerable to active sensor detection.
But only needing one jump ship design, and one that could be built in civilian shipyards at that might be worth it.
I think I would name the jump ship class "Dragoon", or some other mounted infantry name. Some unit that rides to battle, but fights on foot. And I am wracking my brain for a 15-16th century German unit name for the soldiers assigned to hold the horses for their fellow mounted infantry.