Not sure that it is a 3CX issue per se as it appears to me that the limitations will be associated to the Wi-Fi network and its ability to have full facility coverage with no weak/dead spots, seamless hand-offs between access points and that the roaming can be more stringently controlled.
I think that if you can provide the stream of data in a consistent, error free environment, then 3CX can handle it. The problem is getting a network like Wi-Fi, which was never designed for roaming voice (or roaming anything), to accommodate it. I am led to believe that there are some controllers or such that are now available to help in this regard, but I have no experience with them.
As of late, there is at least one DECT solution that allows for roaming and hand overs and the like. I have no idea of cost, but what I do know is that my handheld experience with Wi-Fi versus DECT is that the DECT handsets had better range and penetration capability than the Wi-Fi handsets, so I guess there is a possibility that the cost gap might be less than it was given some scenarios.
In any event, good luck with it and if the 7800 or other Wi-Fi solution does fit your need, I would really like to know as while I don't have a prospect lined up that has this need yet; it is bound to come sooner or later.