Project terminated and operationnal.
I can tell you, nothing to compare with my old Alix board.
I bought a mini PCI-Express AzureWave AW-NE772 with Atheros chipset (A B G N) and it seems to work well. Announced 2.4 gHz and 5gHz (don’t tested yet).
I installed a plug for a second antenna and installed 2 6db antennas on it.