I think there's a couple of things you could try:
If you have a lot of potions kicking around, you could risk wishing for alchemy. Eventually, this will allow you to make potions of youth and longevity. Potions of youth often require somewhat rare potions (extra healing, strength, cure corruption...), but the components for longevity are usually not that uncommon. Blessed youth only reduces age by something like 10 years, whereas longevity increases your lifespan by ~20 if I remember correctly (can someone confirm?). So if you don't want to wish for alchemy, you may be better off wishing for potions of longevity rather than youth, as these may increase your lifespan more than youth will reduce. I don't know if longevity with reverse the "old"/"very old" effects... it seems reasonable that it would if you drink enough of them. I don't know how many of these potions you get with a wish, which is another consideration.
Remember that you will likely have to pass the vault on the way up from your final dive, if nothing else. Ghost lords cannot see invisible, which may help you get through some of these tricky areas.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.