Yikes, that's a lot of money for such a small speaker
If it were me, I'd use the new SB satori ring radiator tweeter in a custom milled maple burl waveguide from TN Allen over on techtalk. Then I'd cross over around 900hz to an 8" scan revelator or something like that in a sealed 0.5 cu ft box. Cross it to your subs around 60 to 80hz. But that design doesn't exist
As a kit or something with a design, I'm not sure what's out there. Most high end designs like that use a 7" woofer and flush mounted dome crossed around 2khz. Not a good idea imo. If flush mounting a dome, it's gotta be a 2khz cross over with a 5" woofer. Maybe there's a high end MTM that does this. Even, so, I think I'd spend less and get the alpha 8 before doing that. Check out the Aurora by Pete Schumacher over on tech talk. Not sure I spelled his name right. He's pretty fond of that design. It's a high end bookshelf and design well I think. He doesn't have much data on it other than a few FR measurements.