Note that the Deco series from TP-Link already supports indoor mesh networks.

I would vote against meshing for indoor EAPs due to limitations of the 5 GHz band if used indoor. We did implement 802.11s meshing on our TL-WDR4300- and Archer C7-based hotspot systems running OpenWRT in 2014 already, but had very bad throughput with mesh networks indoor.

OTOH, for outdoor installations based on EAP225-Outdoor, meshing is a very useful technique to build up City WLANs, provided that there is a free LoS between the EAPs.

So, if meshing is coming to indoor EAPs, it would make sense to add a feature in Omada Controller for disabling meshing on a per-EAP or per-wireless-group base. At the moment, it only can be turned on/off globally for all EAPs of a site, which means you would have to set up not only two wireless groups, but two sites per hotspot: one with mesh enabled for outdoor EAPs and one with mesh disabled for indoor EAPs.

Just my 0.02 cents.

Example only 1 device that can extend the Wifi trough Mesh in stead 2 to support Mesh in the first place.

I see. But this won't work since TP-Link's meshing protocol is proprietary, not 802.11s according to the answer from tech support I got recently. You need at least two or better three TP-Link devices to build a mesh net between them (with two one would be just a repeater, not really a mesh net).