I don't mean to imply anything negative.
You are in business to make a profit. It is only common sense to look for a product that meets your
requirements, at a price that you can make a "decent" profit on, while still being comparable to market prices.
I wish you all the luck. The market is pretty saturated right now with mods, and they all fall pretty
much within the 4 basic types of mods. There are a few unique ones that combine 1 or 2 attributes
from the 4 basic types. I have a few ideas that I don't have the tools to fab, but the only thing
unique about them is construction.
For my 2 cents, I would recommend a single batt booster mod like Breaktru's .44 Mini Booster.
A lot of people said they wished he would make them because they wanted one.
The single batt means it would be easy to put in on board charging.
The PT function would still be debatable though.
Something to consider; I think it was Java that pointed out to me that a charger does not have
enough oomph to drive an atty. When the USB Ego is plugged in it is charging until you vape
and then it is drawing from batt. This sounds perfectly reasonable, but it implies that you would
not be able to run your batt down while mobile and then just plug it in and vape.
PT's with inline batts are not too common now, but I believe I read some instructions a while
back that said you had to charge the batt fully before using as a PT.
Anyways, sorry for the ramble, Good Luck