Does Stacking Wireless Speakers Sound Feasible?

One technical concern is that KEF embeds an "identity" code in the transmitted signal that keeps a stereo pair "private". Like using two identical subwoofers with remote volume adjust, there has to be a way to adjust volume one-at-a-time. Some remotes have an A/B switch to keep them separate. Like I said previously, I don't know what operating system KEF is using.
As to your stacking request, I'll gladly accept any contributions to make this happen! I suggest you send a pair of LS50s to "get the ball rolling"!

I think Tekton has dispelled the Comb Filtering myth...

What Tekton does in effect, is combine the output of the outer tweeters to function as one large mid-range transducer. The outer tweeters do not play the upper freqs, only the center one does. Because mid-range freqs are a longer wavelength, they’re less susceptible to comb-filtering effects when placed close together. If all the tweeters played the upper freqs, then the DIs and others using that array would indeed suffer comb-filtering effects. The main issue with stacking LS50s is the proximity of the tweeters.

The LS50s are capable of such wide dispersion that I can’t imagine you’d hear any subjective benefit from stacking a pair other than loudness.

Yes, loudness. That's what you pay the "big, big" money for (thanks Alex). Loudness and scale. Also, I never said I'd put them one-on-the-other. They could be separated by 12 inches or whatever. So in a room with eight foot ceilings, you could have a seven speaker array. Bet you'd get good sound out of this. Attention KEF: Please have this setup at AXPONA, O.K.? You'd sell a lot of speakers if this works! Remember: You start with a mini-array and add-on as you can afford. You could also sell the rack to attach them to.

That would take about $3400.00 to test. Me personally,I'd just spend that money on a pair of floorstanders. I guess I'm not very adventurous. 

KEF has a new wireless speaker, the LSX, that retails for $1099/pr. Street price probably lower. Saves $1400 from your test. Also, these are powered speakers, have a DAC, and support streaming services. Not to mention the space savings and aesthetic considerations. I think this is a good idea all-around as long as everything works in sync.