Whatever you do don’t make two versions! Save yourself some time and money, there are always people wanting higher voltage or higher current but that will still be true even if you make three versions. Now for my opinion on voltage:
I think it’s best not to look at what voltages people are using right now, but instead at how we can match available hardware. Let’s look at it this way: what is the KV range of the typical brushless motors we may be using, and what are the typical rpm we may be looking for? the KV is often around 170-300, and lets’s say for servo applications that we are usually wanting 2000-6000 rpm peak (I’m thinking direct driven ballscrews or pulleys for belts would be the most common uses). That would translate to 12-24v. 12-36v seems to be the most easily available power supplies as well.
So my vote is for something around 36 volts, with higher current abilities and cheaper capacitors. maybe even go 24 volts if makes the product cheaper, but since a lot of people are wishing for even higher voltages maybe 36 volts would be the best compromise. Having a voltage that completely mismatches the motor is a bit of a waste. Obviously we can rewind the motors, at least if they are outrunners, but generally I’d say it’s easier to just get a new power supply.
Great decision to have 3 motors per board by the way!
Edit: After looking at the list of recommended motors I’m thinking the current 24v may me best? You can always find a higher KV motor if you want more speed, but the lower KV motors are expensive and difficult to find.