Or, perhaps, buffing "Atmosphere Assault"'s drops a bit. It never drops decent amounts of Romulan marks and if you have a bad round, sometimes "as low as two marks". I am not exaggerating that, either. Or perhaps fixing The Vault Shuttle event so it's actually playable by people who aren't running Delta Fliers and Peregrines in AP and Mk XII rep gear.
Even better, more new content against these two neglected enemies, the elachi and tholians, that gives better rewards, seeing as both were just kind of brushed aside in favor of the voth and borg, respectively.
TL;DR-- Most certainly agree with OP. Romulan Marks are a pain in the rear to get compared to everything else--and chasing rabbits, to get at most one Eppoh every five days (often less), which MIGHT give you 200-400 after another four days... is not an answer or a solution.
Romulan Rep NEEDS more ways to make Marks, and upping the challenge of existing Space missions should be easy and simple.