Given that this is a private project and development of new content is not to be expected on a large scale, it is probably an idea not far fetched and probably considered already by the devs to reuse existing content.
For example i dont think anyone does Sydonai runs given his rather limited loot table. Yet he is one of the more unique Bosses - so giving him a better loot table would revive the run.
Occulus and Abby might be worth a run for the few low level items that are worth to farm but they are no challenge at all.
What i have in mind for them is put them in the higher level original Hellgate Maps in the form of Hellrift Bosses.
Imho now that mods are being farmed in the Catacombs (which i like very much) and Brompton or maybe luck runs on chests in wake hollow there is little incentive to do hellrifts. But i think it should be cool to find a hellrift and then ancient blood. Putting one of the not used bosses into the Ancient Blood with a decent loot table would be cool. An idea would be to include the good low level items that people are now farming by doing even maps in normal (sues, duellos, that evoker belt etc.).
Another thing for ancient blood would be a type of setting where exceptionally high numbers of mobs spawn, would like that too. Kindof miss the first Necropolis experience where you need to hold of the masses.
Also another very motivating (but maybe a bit offtopic) thing would be quests giving you a free Aug. Augments are cool since they produce unique items. But i think they are too expensive. it doesnt neet to be the leg aug but enabling players to get upgrades for gear more often is not a bad thing and it can go wrong too. Could be a reward for the Sydonai thing as it is a rather long run. Might be overpowered but just an idea.