First of all, i have never used OpenWrt and still a newbie on linux and network configuration. But, i need something a bit special for a client. At work, we design and build all sorts of wastewater pumping stations and potable water distribution. And for one client in particular, we are building mobile units that goes all around the world. I need a router that can be used as a wifi client mode, which mean i'm having my own subnet, dhcp and routing table, but if wifi signal is not strong enough in this particular place, they will be running an ethernet cable and plug it into the wan port.
I'm wondering if it is possible to configure OpenWRT to be able to accept either of wifi (in wifi client mode) but also thru the wan port. Both would need to be on DHCP on the wan side, and i would have my own lan subnet. On top of that, i would really like not having to change the configuration whether it is wifi or wan port and have it fully configure to accept both because it might be different from place to place.
I hope my explanation are clear enough and really hope there's a way to do this.
Also, I was planning to buy this [https://www.amazon.com/dp/B07712LKJM/ref=psdc_300189_t4_B01EVI1YVA] for this purpose, what you guys think of it? I need the smallest router possible with at least 3 ports.
Thank you very much!