This implies you might be thinking of amplifying the video transmit signal at the craft. Be careful what you wish for. If you boost the craft video signal you could potentially start losing your control signal first, triggering RTH. Is that what you want?
If I can get out to about 3miles reliably (stock battery can't go much further) without boosting the craft video signal, I'm good. I'd rather be humble with 3mi and have control of the craft, always losing video first as a warning, versus flying out 3-4 miles, having video, but losing control signal all the time to trigger RTH. I think that's a recipe for disaster, however the few times my RTH kicked in, it returned to papa without a hitch. The problem is waiting and waiting for RTH and to regain control ages me.