Tell us more about your objectives. Communications, cold water, contaminated water, added safety in a blackout, deep air or Trimix, rebreathers? Nothing is free and there are no perfect solutions to anything. Have you considered the trade-offs such as breathing down your supply on long surface swims, vomiting in the mask, switching to alternative air sources (expensive switching blocks), proprietary regulator repair issues, and second stage failure?
Have you looked at the Kirby-Morgan
SuperMask and
EXO-BR? The EXO has spectacular regulator performance and the SuperMask allows rapid regulator removal. Also, a much less expensive option that may suit your needs, has been around for 50 years, and allows you to use your own regulator is the
Cressi Full Face Rubber Mask.
For rebreathers, definitely look at the
Dräger
Edit: I forgot to mention dead air space. CO
2 buildup is an issue, especially for shallow breathers. You really need to develop a habit of deep slow breathing on a FFM or commercial hat with an oral-nasal. Of course, the Cressi FFM does not have this issue.