The idea is a ghast saddle that provides minor buffs to the ghast like speed or health. It could even drain nearby source jars to heal the ghast. But the main thing is that it would be configurable in an equipment table with the ability to add threads.
I'm currently playing FTB skies 2 which uses the happy ghast as an early game transport and exploration solution, I just wish it was a viable option even as I progress through the pack. If I were able to make an enchanter's ghast saddle once I get an EA up, I could slap a Starbuncle thread on that bad boy and have myself a midgame transport option.
The main problem I see with this is that it would lack the same personalization options that the armor has, mostly due to the lower thread count (even if it can somehow hold more than three). The main thing is that I can't imagine there will be many threads that actually have a practical use (what would thread of spell damage do for a ghast anyway?). This could be solved by adding ghast-specific threads, but even then what qualities can be enhanced other than speed, health, and carrying capacity?
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+ health pot, and Ritual of Restoration