We discussed my question today in the Kollel:
To answer this it's essential to define the purpose of a Chuppah. Unfortunately, we don't have a clearly defined one, as different Rabbis connect it to different ideas and traditions.
I would argue, that the contemporary Chuppah, as described in Remo (Eh"E 270) serves the only purpose of the public recognition of the couple's intentions. I.g. "if you want to propose and your intentions are true - show it buy stepping under the Chuppah".
Imagine a crowd of hundreds of people, how would they know who's getting married? You raise a tent or just a canopy to signal everybody "it's here", "this couple is getting married".
If so, the tent must be visible to the crowd and associated with the event. I accept the Talmudic claim about the height of a Kosher Succah, that's limited to 20 Ama because beyond this our eyes don't associate it with the place. And therefore assert that in order for a Chuppah to be perceived by the crowd, its height must not pass the 20 Ama limit.