Your first paragraph is possible now with most enterprise 802.11ac equipment (Cisco, Aruba, Mist, Ruckus, etc) but it needs to be properly designed, placed, and

Your first paragraph is possible now with most enterprise 802.11ac equipment (Cisco, Aruba, Mist, Ruckus, etc) but it needs to be properly designed, placed, and configured. DECT is a different frequency and is much less vulnerable to nearby metal, backscatter and so on. You need to get someone in there who is competent at wi-fi design (I am only marginally so, but I’ve done a lot of learning by failing)