I have thought a lot for this topic and actually have 2 lights with rear clicky and charging, one custom and Amutorch jm70. There are 2 issues - if you want charging to work, you have to turn on the light - this is difficult to understand for the regular consumer. The other thing is, that the light will get taller due to charging circuit. I am still thinking how i can get around this, but the only working solution i see is similar to Olight implementation - rear eswitch, that will solve both issues, but you move far away from budget light.
To stay on the topic: own brand is the way to go, and even better own hosts, not just branding, but that requires certain single order volume.