The FCC regulations are troubling, especially with how companies like TP-Link are reacting, complete cooperation and compliance. At least, however, they're being honest and telling us when and how they are changing what they do, which you can bet other vendors won't do. There are several OpenWRT capable router/APs made by TP-link worth buying before the April deadline.
My router is a $50 3.5" SBC, old fashioned PC BIOS (no UEFI or intel management engine) with a single core Atom processor on it, dual GigE, and a Mini PCI-E Wifi N card. It even has a SATA port.
It runs Debian 8.2 on a 4GB Compact Flash card with 1GB or so to spare. I have no doubt a BSD would work, though not sure about wireless support there.
I looked long and hard for am ARM based system with u-boot (objective: FOSS all the way down), but one cannot be found with dual gig-E for less than $200, much less one with Mini PCI-E slots and expandable RAM. (Any VCs out there want to start a company making MIPS/ARM FOSS routers with dual gig-E and mini PCI-E? I am a system board designer...)
The actual router work is done using Uncomplicated Firewall (UFW), hostapd, and dhcp server from the repos. Debian 8.2 with systemd building a software router easier than it was for me using Ubuntu 14.04 or Arch because it had all the software I needed in the standard repos that are current.
The drawbacks are: it takes a bit to get the configuration the way you'd like, and setting up packet forwarding with UFW is not obvious (the alternative is an iptables script that is more work than a non-network guy like me is willing to do). The biggest drawback is non-AC wireless. There are Mini PCI-E cards out there, but it is not easy to find a Master mode capable card that doesn't require a proprietary firmware blob.