Does Stacking Wireless Speakers Sound Feasible?

What you'd end up with is a bunch of comb-filtering and wonky frequency response with huge peaks and valleys. Not because of any wireless signal issues, because of the proximity of the baffles and tweeters. This would be true for nearly any speaker setup that wasn't designed as a line array. 

The LS50 baffles were designed to minimize baffle reflections and stacking them would only serve to nullify that advantage. 

That said, stacked speakers can make for an interesting sound, but not one that's accurate or low in distortion.

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.