I can design one for you and you can have Don build it since he is closer to you than I am.......(just a thought). And I have done spherical enclosures before, but the benefit vs construction is not great for anything but mainly sealed designs due to decreased resonances(not very noticeable at lower frequencies as you may think).
As far as air movement is concerned, I have to chime in on this if you don't mind. There are two different types of related sound effects that occur in a port, regardless of its construction. Moving a lot of air does not mean the design will produce an audible authority. It only means that the pressure build up into another adjacent "cabin" will substantially increase due to resistance equalization (coupling). So, having a design that is based on moving a lot of air is not generally for those who want something to be musically "loud". But if you are looking to enter some comps, or impress your friends with a groundpounder or low end monster (which, by the way, is not really driver dependant), then by all means, couple the hell out of the port.
But for musical authority and intensity, generally, a larger port is recommended anyhow, NOT to be confused with an spl port (again, different sound concepts). And also, not to be confused with using minimal port requirements to reduce port noise but maintain pressure. If you have ever wondered why horns became so popular once again, it is due to the ability to produce a propagated wave that couples in intensity much better than in pressure...and your ears will tell the difference. Here is an example (which I have mentioned before on a thread a few months ago)......
Take your hand and place it in front of your mouth and blow out some air and you can obviously feel the air hit your hand. This is the spl concept of coupling. If you open your mouth larger, it take more pressure from your lungs to produce the same pressure as before(usually in hand with power in the audio world). Now, if you produce a humming sound, you will notice that this does not directly effect the pressure related output significantly.
Because this is the intensity based output. And not all times are both needed for a "loud" setup. In fact, pressure in this case is not a major factor in audible loudness much at all.
So, if you are humming a tune and you stop blowing air out of your mouth, the sound will either sound "cleaner" and/or stay constant in output if everything else is constant.
The main difference in this example from audio, is air is needed to vibrate your vocal chords, so naturally, the more air you push out, the louder the chords will resonate. In audio, this is related to electrical setup instead, so power is a factor of "audible loudness" as well.
But the point is, to never confuse a ports characteristics in the type of port it is, with pressure vs intensity as the two are different factors in audio. That said, it is not always going to be the case that rounding the edges will produce a louder output because the air movement is not a base of intensity, it is created BY mechanical movement, so by numbers, the design will produce likely more "spl" than intensity.......again two different factors.
But if you have to worry about port noise, you may want to consider changing the limitations of the design to accommodate more space for port area if required. The MAIN concern with port noise should lie in those interested in figuring for throat constants for horns and such rather than conventional designs with constant port area, as the horns throat can be and will be significantly smaller(in most cases) than the mouth, or opening of the port to the cabin/trunk/room/etc.).
So, if you are looking for musical output, worry less about rounded edges, and more so by avoiding port noise by means of other ways that are going to be more important than "hiding" the effects of port mach physically.
Just my thoughts on the subject...........