The problem isn't a lack of software to put on hardware, it's a lack of hardware that doesn't go out of its way to thwart attempts to install different software, either intentionally or as a side-effect of being optimized for cost.

As an example of the latter, I have a Monoprice-rebadged Tenda W301A ceiling-/wall-mount AP on my desk. It only has 2 MB of flash and 16 MB of RAM. It has a TTL serial port, but the lines are broken out to surface pads that aren't even grouped together on the PCB. (They're not labelled on the silkscreen, either.) The version of u-boot it ships with is stripped down to nothing, probably because of the limited flash space available. For ≤$5 more on the BOM, these problems could be fixed, and the device would be considerably more useful.