Very impressive. You asked for suggestions / what we'd like to see, so I have a couple things to I'd like to mention that have been on my mind.
1. Configurable sound interrupt parameters
In regards to blaster block and lockup, I'd like to have not just the wavs configurable, but ideally their behavior. That would include adjusting flicker effects (which the Ultrasound, and to a greater extent the PC and Crystal Focus currently allow for), but also the ability to choose whether or not they can be interrupted by other sounds, like clashes and swings. Keep in mind that for maximum openness, not all users will necessarily use the blaster block / lockup slots strictly for blaster block / lockup effects. Or they just may or may not want their blaster block effects, for example, to be able to be interrupted by clash and / or swing effects for matters of personal taste. Or they may just want to ditch the blaster block and have two different kinds of lockup effects available on the fly for variety's sake. I don't know about the Crystal Focus, but to the best of my knowledge the Ultrasound, PC, and MR boards do not allow you to adjust which sound effect can interrupt which. Instead, they are set at what are generally very sensible, logical choices: blaster blocks can be interrupted by clashes but not swings, lockup can't be interrupted by anything. But personally, I'd rather have two totally open, configurable sound files whose interrupt parameters are totally configurable, rather than two which are optimized to serve as straight blaster blocks / lockup.
2. Unwanted swing sfx activation control
The other issue I wanted to address is the problem of activating unwanted swings, which you get when using the rolling ball swing detectors used on MR and PC boards. If you plan to go with an accelerometer, like the CF or the Ultrasound, this problem is pretty much solved for you. But if you will be using the rolling ball setup (which will, on the positive side, allow you to control price a bit), then I have a suggestion. I'd like to see momentary swing deactivation available on your soundboard, such that the user could depress a button on their hilt which will make swings impossible to activate while held down.
Why? So that when you are just standing there, or walking slowly with the hilt held in front of you, you don't hear the hilt go "whoosh - whoosh - vim - slash - whoosh!" just because you breathed or turned to look at your brother. There are many great moments in the films where there is a break in the fighting and the two opponents are squaring off, measuring each other, pacing slowly, etc., and all you hear is the quiet hum of their blades. That's hard to achieve currently with MR and PC boards.
There are two ways you could implement this. One would be to have an additional sound slot configured (or better, configurable to be) like a lockup, featuring a duplicate hum wave. When depressed, this would produce a hum sound that could not be interrupted by a swing or clash. (In fact, if you commission a PC board from a smith, you should be able to do this now (not on the TCSS ones) by substituting a hum wav for your lockup. It's just that you'd lose the lockup.)
An even simpler solution, as I was advised recently, would be to just put in a momentary / latching switch that opened the circuit of the swing detector, effectively deactivating it for as long as the button was depressed. A very easy solution, and one that could potentially be applied to any sound board with metal ball swing detection (although not without monkeying with the board and thus invalidating your warranty if you're working with a PC).
When the swing is fully active, of course, this solution still won't give it the precision swing registration of a CF or Ultrasound. But this workaround would get rid of the most annoying problem, the activation of a flurry of battle action sounds when you're just standing there doing nothing. Again, this fix would likely work on any metal ball swing detection sound board, but since you're still in the formative stages, you could integrate it more elegantly if you were so inclined.
Anyhow, that's my two cents. Best of luck with your new board. I'm definitely interested in seeing your progress.