What are some good bloodlines to temporarily have using an Ampoule of False Blood and Eldritch Heritage ?
The Impossible bloodline would be good for periodically crafting during downtime.
Verdant imp. EH allows at-will plant growth which could be useful to fortify an area, or to make friends with people.
Arcane IEH might be useful to learn a spell temporarily. Rakshasa (at any level of EH) might be useful when doing something sneaky.
The 20K cost is a real limit on how much use you could get out of these relative to simply buying expendable magic items though.