Hmmmm,didn't know you'd worked at a Nuclear Plant for any time
To address each of your heads needs in order.
Selling mods to Joe Pubic first.
I doubt that 18650's are going to remain as the main source of portable power for much longer,we are already seeing 26650 mods appearing and I recall reading something somewhere that battery technology has recently jumped one of the major hurdles with batteries(big power output meant big physical size)as they were talking about large outputs from hearing aid/watch sized batteries(though this large output might've been me dreaming)
My Vamo arrived with 2x18350's in the box,so people are obviously happy to stack small batteries.I'm not going to list all the mods that take 2 stacked batteries as I'm sure you'll still correct me in places.I also know of mod builders that offer a return it & have their mods repaired service,as there is no obvious method to open it up (due to the powder coating/paint finish covers the screw heads)so if we built a box mod which had a socket through which the device gets charged,and added the correct charger to the final product packaging,solving that issue.
As for trusting people with LiPo batteries in case they cause them to vent,the media is in love with quoting scare stories about "Mrs Braindead bought her ego from a yob in the pub whilst pissed out her remaining brain cell,left it plugged in for 3 months & it exploded & set her council house on fire" So,if creating a mod with LiPo cells kills a few of the "stupid people" gene pool the world becomes a nicer place.
My mods are intended for me alone anyway,if asked I would build one for those that requested it but I would also expect them to understand the risks with the batteries and not plug it in to recharge and feck off on holiday/take dog for walk/go to bed etc.
Sigh,that's the problem I have.With only one head,I just ramble on and on in the hope that it makes sense eventually,but not this time.I can see the problem though can't figure out how to fix it.I started with a "first" and can't see a "second"