Okay so I may be wrong but, from my understanding of mdma the reason the comedown is alot longer than like speed for example is because not only does mdma deplete your seratonin, but im pretty sure it inhibits tryphtophan hydroxylase for a much longer period after youre no longer high. like 24 hours+ so not only are you out of seratonin, but unless your taking 5htp your body cant turn tryptophan from your food into 5htp and then seratonin.
anyway this relates to your post because the oxidative stress caused by mdma on the synapses in your brain im pretty sure is caused by dopamine being catabolyzed by enzymes which are meant to break apart seratonin. what happens is as the dopamine breaks down it it produces peroxides from those hydroxyl groups. if you take vyvanse youll be increasing the dopamine, and probably the oxidative stress. i would wait atleast 36 hours or take 5htp before starting vyvanse. but im sure it's not going to do you that much harm
as for letting your receptors adjust, i dont think thats very important to worry about. they adjust for a reason. your body will bring them back to normal, maybe slightly slower with vyvanse