I considered this as well, because there seems to be a lot of interest in Columbus (OH), but that also seems to be where it stops - passive interest. I haven't proactively advertised or tried to make a sale, but I have been in the community workshop building the hot rods for the past two years. People oooh, ahhh, and wow (literally just heard a "Wow!" a couple hours ago), but never even express the slightest interest in even learning more about it. I figure a real potential customer would have asked me about building one for them - nothing. One guy, who is a fellow business owner here, has a Mini with a blown head gasket that he wants to convert, but he just asks really general questions about doing conversions (Is it hard? Is it expensive?), and has never even asked me to sit down and go over what it would take, in detail, with him.
There are, however, a handful of Priuses and Volts in the parking lot on a regular basis, and I suspect that the prepackaged, easy, way rules here. In fact, in the almost five years I have been here, I have met two other people who have actually done a conversion, and very few who have thought about it.
I've also noticed that I never really hear much about cars that were converted by a "pro" shop; in the news or here on the forum. I know this is DIY, but there are people here with production EVs, and people who have purchased an already converted EV and want to upgrade or learn about them. I don't remember ever reading, "I purchased this so-and-so, which was converted by XYZ EVs, in Timbuktu. How do I..."
Finally, in comparing this whole cottage industry to the hot rod industry, from whence I come (there are a LOT of similarities): The hot rod industry is fueled a lot by people wanting to recreate the past, whereas EVs represent the future. There are a precious handful that want to recreate the past with future technology, but the field (of prospective customers) starts to get pretty narrow. With production EVs ramping up, it will be a hard sell (IMO) to get people to make such a huge commitment and investment, when there is very strong, easily obtainable, competition in production vehicles with the absolute best of the best technology. A more feasible commercial venture might be in servicing and upgrading those vehicles down the road.