OK - I wasn't sure about the material used, and I'd like metal more than polymer.
If you make them to use standard "grommet mount" or "surface mount" lighting, you'd be able to sell them for less bare - many of us are within rage of a heavy truck supply house (I can throw a baseball into the parking lots of four or so,) and come out ahead.
I'd also think you could come up with some manner of using Delco Weatherpacks (or similar) to adapt the lighting to the vehicle wiring - this would entail some "clip & crimp" on the part of the owner, but the Weatherpacks would make things simple, and would feature a sealing connector.
If you could add a "baseplate" of some variety (light-gage should be OK - say, 18 or 20 gage steel or aluminum) you could replicate the sealing "bootie" found on the OEMR light assemblies and tackle the sealing that way - which would allow you to reduce the cost of the adapters 9Weatherpacks are spendy - Molex would be cheaper...)
If you'd like to bounce ideas off of me, I'm available backchannel - and you can send some sort of NDA along before we get started so I don't go in and undercut you (I'm in the business of making upgrade parts myself, so I'd understand if you want to protect your ideas...)
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