You could do that, it would work, although I would let the runoff go to waste rather than back to the reservoir. Coco works best as run-to-waste, the idea being that when it’s watered any nutrient buildup gets flushed out. I like to think of it as flushing through with fresh nutrients at every watering. I’ve also found that coco likes to dry out quite a bit between waterings, so no need for multiple waterings per day unless you’re using tiny pots. With 5 gal I think you mentioned you could water thoroughly until 10-20% runs off every other day.
This is pretty much what I’m doing in this thread below. Except I use self watering planter pots. So I put about 2L through them every other day and I let the runoff go into a bucket. If I’m going away for a day I can also fill up the reservoir in the bottom of the self watering planter pot. I let them get pretty much bone dry before the next watering.