If you need to do this and is using tftp server from cisco linux you have to open a TAC case on this and instruct the TAC what it is you want.
Former I have been abale to get the root password acount decrypted and do this my self with in 30 days. (the default lifetime of login).
Now Cisco TAC do not give the decrypted password out but do this.
This will create downtime but will be better and do not need TAC access.
I have had som dificult when I told a UC guy that I neede seval WLAN config files top be uploaded and he said only config files starting with SEP schoul be on the CM.
After som time I showed him that it worked by uploading 2-3 files by hand and restarting tftp service everytime.
It would be need if the Cisco UC CM understood a tar file and could extract the files and give them the right prmission og ownership.
But that smart is the CM apparently not.
I had allready uploaded the tar file with the many config files to the tftp server.
When I had the TAC man logedin I did a search to find out where it was and dit the extract and chown and chmod. and the restarted the TFTP server.
There is a bug with the cisco Linux TFTP service so you need to be running at least 1.3.4 or higher on the 7921 & 7925 phone to support this else the phone keeps downloading the config file until you give the new option 150 and never registret to the CM as long the files is on the tftp default share.
or you have the upgrade the phones first and then do the wlan config deployment.
An alternative solution with out TAC would be to create another TFTP server that you control 100% and point to that one with option 150.
when the user have downloaded the config files you can point to the orginal again.
It is only when you have changes to config you need config files for WLAN.