I over came decades of suicidal depression (as well as schizophrenia and bipolar) with a self concocted protocol which included psychedelics and now don't take traditional meds.

I read the OPs intention as "use K to get the person back from the bottom of depression and then leverage that boost in mood to start a habit of excersize"

That seems reasonable and a good approach. You want to reinvest the motivation and better mood into relationships and behaviors that will continue to compound feeling good.

I'd also recommend Gratitude as a practice and ultimately some sort of somatic work where you are encouraged to go deeply into any uncomfortable feelings with your full body.