Look, you're making this far too complicated for yourself. First of all, go ride the bike you have on the trails you intended it for and see how it behaves. Then do it again a couple of times because you have to get used to the new bike a bit before you can judge its performance fairly. Maybe you will learn that the bike is already capable enough and the story ends there with no loss for you.
If you still feel like the bike is performing inadequately and it's definitely not working out, order a Tyee frame with a shock + pick out the fork you want for it. Then put up the Hugene frameset for sale - you can list the fork both separately and as a combo.
If you hurry, you can still pick up the Tyee frame with a sizable discount and have it arrive by the time you will have hopefully sold the Hugene frame and you're good to go. The other parts are going to fit on the Tyee frame anyway.
Take this as a lesson for the future and keep it simple for yourself. It's unfortunate to have a bike that doesn't fit what you want to do with it, but currently all you have is a suspicion that you really should confirm or disparage first. No need to go into this as if you're reenacting the sufferings of young Werther
Good luck!