The point from tux that the efficiency at 93 is enough imo is right. Nobody here runs runs amps which would benefit the 99 part (ok, someone does use tube amps, I know many at klipsch forum do).
While I readily admit I have no design experience and dont fully understand all the tradeoffs of various tweeter models, I'll say this --
The brilliance of Diysoundgroup, beyond the selfless efforts of Erich and team, is the waveguides.
Except for buying an expensive JBL speaker, where else can you get them? Klipsch horns have excellent directivity...I own many, but none match the SEOS.
I would focus the site into iterations of those beauties. Floorstanders and monitors, even bookshelf speakers (true ones), if the design allows for it.
I havent heard a speaker I like more than the HTMs. I've heard most of DIYSG and many major manufacturers.
Few people, even on this site, really understand the value of those guides.
There are htm6 10 and 12.
I would add the 8, and then create floorstanding models of the 10s and 12s.
Htm6 (bookshelf), htm8, htm10, htm12
Fhtm1010 and fhtm1212.
1099s, 1299s, 1899s are glorious and specialized for 3 way or music lovers. Waveguides here too of course.
I would also make horizontal centers for each that solve the lobing problem like the 1099 did.
Those I would advertise beyond DIYSG to the general public....since almost nobody has access to good center channels without lobbing effects.
But then again, I've been known to offer my 2c in many places it wasn't asked.
But I know Erich listens, whether he agrees or not, and I like that part the most.
Option1 - build yourself
Option2 - Erichs team builds and offers finishing (some veneer options would blow people away)
Theres gold in these designs imo