The goal is to get to lvl 12 (8 Preacher, 4 Synth).
Taking the Heroism domain.
At 12 lvl the first round of a combat looks like.
Aura of Heroism swift and Haste or Prayer.
Along with the benefits of not caring about your Str/Dex/Con and having a nice boost to Natural Armor Synth brings some great buffs before getting the magic level 12. Also great skill monkey potential.
Preacher lets me continue to be 'that guy' by forcing rerolls on hits to the party along with bless, heals, and some decent damage output via judgment.
Without really building it out looking at something like 13 Preacher, 7 Synth at 20.
Don't completely ignore your con. You'll need real HPs to keep the Eidolon suit alive.
What's the flavor for this build? Crunch looks good, honestly you can't really mess up a Synthesist. Which deity? What's the eidolon look like?
Check on the Con.
The flavor is being close to bard group friendly but less nancing about. A bit more smashy but lots of party stuff. It is a custom world so no deity anyone would recognize. Still deciding on if I want to go ranged or melee which would change how the Eidolon looks quite a bit.