Hi Franz -
there are certified devices out there, running OpenWrt / open-source drivers. May I ask, what particular regulator issues you have in mind, that a open- source driver can not comply with? Read: Are you sure you don't get the regulators blessing for your product with a open-source driver?
Besides: Do you know this song by Eric Idle, regarding the FCC?
http://www.youtube.com/watch?v=F4ajZ-5kTXk
A few memes:
Any product can be tampered with.
In many certified devices you can simply switch the reg domain. Then choose Japan, for example. Now you can transmit on channel 14 in the 2.4GHz range. Not so legal anywhere outside of Nippon.
The old Broadcom chipset / proprietary driver can be configured to transmit at 250mW with the proprietary closed source driver. Hence you can transmit at ~25dbm EIRP (with the stock antennas), far beyond the ETSI regulations of 20dBm EIRP.
Any device with a external antenna connector can be used together with a high- gain antenna. Again you get far beyond the legal limits.
Cheers, Elektra