Maybe you could have the Sayans as really annoying bosses throughout the beginning then bring them back when the player has a good enough arsenal to take em out easily, making the player feel happy at their awesomeness.
You know, my mod is on hold to be delayed. I posted the announcment that it was delayed a fair while ago, my Mum's moving houses and we might get rid of this computer and get a new one as we move. We still haven't moved yet (Still house hunting) so progress hasn't been delayed yet. Anywho, don't forget to write down what your working on before you stop, you'll save a lot of time that way.