Or, if taking Odin and Alexander off 2hr doesn't float your boat, how about making a job trait at level 75 that makes the normal avatars (carbuncle, Ifrit, etc.) 2hr blood pacts available all the time. Seeing as Odin, Alexander (and i assume Atomos when we get him) will take over the 2hr ability attacks, and by level 75 the 2hr blood pacts aren't much more powerful (if not less powerful) than high level black magic.
They would still consume all MP and work exactly the same as they do now, they would just be available whenever.