I think that fairly high-output speakers with a smooth power response would work best in a room that size. They can be narrow pattern or wide pattern, but the point is unless you listen nearfield the reverberant field's energy will dominate the tonal balance. The on-axis response will be relatively unimportant; it's the power response that will matter the most.
The "power response" is the summed omnidirectional response, and smooth power response implies a fairly uniform radiation pattern up and down the spectrum. It can widen at lower frequencies, but we don't want any significant narrowing or blooming of the pattern in the midrange or treble (though some beaming in the high treble may be unavoidable).
Also, it would be nice to be able to adjust the relative level of the highs and lows. Bass is probably swallowed up in that room, on the other hand sounds like it's a fairly "live" or possibly even "bright" environment.
I would not have expected a hybrid electrostat to work well in such a space, as the radiation characteristics of the woofer and panel are fairly dissimilar, and equalization cannot correct radiation patterns. Something like big Tannoys or Klipsch Heritage speakers are imho a better bet. Big Maggies are another possibility; they have good power response. If you are a recent lottery winner, then maybe even the MBL Radialstrahlers - but personally I think a narrower-pattern speaker with good power response is more likely to work well.
Duke
dealer/manufacturer