Sounds like you're already moving forward on this for your own use, so I would just say, at this stage, make sure you're documenting everything. Publishing DIY plans won't be too hard when you're finished, and if there's a lot of interest you could move forward with commercialization at that time.
Might be worth investigating packages like the one Brent mentioned in another thread, see how they solve these problems.
http://ronsmachineshop.com/Hidden_Turn_Signal_Kits.html