I thought it might be interesting for people to bring up for discussion things they're planning to do with such boards, so I'll open with mine (which is a few months down my list of projects!):
I have some old small computers that I'd like to fit new insides to. I had been planning to use the Orange Pi for these, but having an open standard board sounds like a much better idea, and, assuming a suitable range of boards is produced, should allow me to pick what trade-off I make between performance and battery consumption.
The main device I want to fit a modern computer inside is a Toshiba Libretto sub-notebook (colour screens of a similar size are available, perhaps something like http://www.pollin.de/shop/dt/NzUwOTc4OTk-/Bauelemente_Bauteile/Aktive_Bauelemente/Displays/7_17_78_cm_Display_Set_LS_7_HDMI_DVI_VGA_CVBS.html if there's room for its driver card); I also have a Sharp PC-3100, which is a thinner device and might not have room (I haven't opened it up yet) and has a strange screen size, and I used to have an Epson PX-8 (relatively large, but with a really strangely proportioned screen) and have ordered one a few days ago on eBay.
I expect a lot of devices like these will have a lot in common, and it might be possible to come up with a common open mezzanine design (perhaps little more than a breakout board for an FPGA) that can be adapted slightly for each of them; keyboard scanning, trackpoint, etc, probably much of a muchness; some might want special LCD drivers for the original screens if you don't fit a modern screen with a conventional modern interface. So I thought it worth bringing up for discussion, as there might be people out there with other devices they want to try something like this with. (Psion 5, or is that too small? But with 3D printing, it should be possible put extension slices into cases.)