Sadly, it would be a very niche market, I'm afraid. Hell, even I'm not that experienced taking measurements with REW, yet. Consider the difficulty people have just doing that! Now, ask them to program a 2- or 3-way crossover!
Regardless, to the first part of your question, the challenge with the passive XO is that every component effectively drains potential power. so a very stylish LR4 Crossover is going to inherently limit power more than the 2nd order version. This is probably only a tiny corner of a bigger puzzle, too. For example, adding resistors to normalize Impedance...
I am trying to weigh the long term goal of my fantasy build being all active or a hybrid with powered low end and passive uppers. You see it in such speakers as Def Techs
or some of Troels Graveson's designs (especially his 4- and 5- way builds.
Towards that latter example, he switched over to using the Hypex Fusion Plates. Check Madisound or Hypex if you want to see their capabilities.
Regardless, even using lower powered or less expensive DSP Amps for each speaker can get stupid expensive. And the range is pretty extreme. (JTR, as an example?
)