If you bricked it with FSM downgrade, all hope shouldn't be lost.
As I explained, the issue should be with the wifi/BT board.
FSM firmware reinstall works pretty much the same as normal update, with a few differences. If there is a hardware issue, it will fail.
Not sure what you mean by "red light screen" though. Shouldn't be RSoD, so I assume when you turn on it just turns back off, correct?
Either way, I suggest you try to install a different wifi/BT board in it, and reinstall the same firmware you tried to install via FSM.
And if you do fix it, just put the original wifi/BT board back in it and give it back to your customer :D
if i understand what your saying just download this file Multiupload.com - upload your files to multiple file hosting sites! put lv2.self on a usb drive with your current firmware as well both in the root of the usb (no other folder) insert the usb into the far right usb and turn it on. you wont see anything on on screen and it will take about 5 minutes too complete when its done it will flash red for about a minute then shut off. remove usb drive and you should be back to xmb.
where abouts do you live? if your in the uk i have many spare wifi boards i will send you one.
Sorry for the thread hijack here, but any other components you have? Like dead boards I could salvage parts off of? Or more specifically the ram chips.