An omni tweeter, especially using the folded ribbon Heil kind, sounds like a good thing. My only concern would be how well it integrates with the rest in lieu of a crossover. It appears to be designed to integrate cleanly and easily out of the box without a crossover with other M&D speakers which makes sense.
I would expect adding to the OHMs would make them sound more like mbl than prior. mbl uses multiple omni drivers including tweeter. mbls tend to need more distance to walls than OHM for best sound since they are full omni. The tweets might as well? OHMs by default can go closer to walls due to attenuation applied to CLS drivers in wall facing irections inside the cans. Not sure if closer distance to walls would be an issue or not with the omni tweets.
I would expect adding to the OHMs would make them sound more like mbl than prior. mbl uses multiple omni drivers including tweeter. mbls tend to need more distance to walls than OHM for best sound since they are full omni. The tweets might as well? OHMs by default can go closer to walls due to attenuation applied to CLS drivers in wall facing irections inside the cans. Not sure if closer distance to walls would be an issue or not with the omni tweets.