What kind of differentiation do you envision for the two classes? I know I personally don't want basically two of the same ship, but one being less expensive and better at what it does than the other.
I haven't really thought much about it yet (too preoccupied with real changes to worry about hypothetical ones). It can be done though. The Nebula is the premier destroyer for the New Republic and it should reflect that. Perhaps the Republic is more defensive and the Nebula is more offensive. I can rework Republic upgrades if necessary.
The cost-efficiency argument doesn't make sense to me - shouldn't an ultra modern, energy efficient battlecruiser cost much more in terms of R+D at least, to be able to bring such a low-cost but powerful ship to the front lines?
It would cost more in terms of R&D - 25k apiece on top of the 20k for the Republic.
This would have to be reflected in unit cost in game, I would imagine.
Not really. Strike cruisers are cheap and ultra-modern.
The Nebula is supposed to be rare enough even during the NJO timeline that only a dozen or so exist, and are held close in to protect the core worlds.
As Tropical Bob says, we don't have to fall into the traps of poor research just because NJO authors did. I've estimated that the
Republic-class was built from 6.5 ABY to 16 ABY (assuming it ended with New Class) and the Nebula was built from 13 ABY on. 6.5 ABY to about 12.5 ABY is pure turmoil for the NR, with repairs delaying the launch of new ships. Even if Fondor was relatively unscathed, Kuat, Sluis Van, Mon Calamari, and so on were all hit. By 13 ABY, the final New Class designs were ready (given the phrasing "almost a decade after Endor"). That's six years of war and six of peace before the Vong invasion. Nebulas should definitely outnumber Republics (by the way, the
Republic-class in NJO is
an entirely different design).
I guess I really don't see a way to reflect this unless the cost of the vessel is substantially higher than the Republic; while the Republic may still be prevalent in NR fleets down the road due to its workman like capabilities (just like Impstars!) and thus not necessarily be replaced by the Nebula, it shouldn't be more expensive than the Nebula for the purposes of game balance, right?
The problem is, the Republic is significantly larger than the Defender. All else the same, it should cost more and have a better hull.
As for pricing, well, I'm not prone to making up numbers. If I can source it as less or more, then that's what it'll be.
Update: it would seem that the 1.94 billion figure is the result of someone being overly literal and taking half of the outlier 3.88 billion cost of an ISD and applying it to the RSD. Using consistent SotG pricing (every other sourcebook lamely writes "not for sale"), it works out to 168,528k for the Nebula and 72,835k for the Republic, which puts the latter in range of Victory/Venator pricing. I'll re-check the stat conversion on that and hopefully get it more in line with those two. That should do it.