I think it would be more of a hassle to convert those Turtle Beach x11s to something usable. Not to mention they won't look like anything used by the military while taking away from your goal of adding extra realism.
If you just want the look without the functionality, you could just get these for cheap. Free shipping.
Replica Bowman Headset -
http://www.ebairsoft.com/ztactical-z027-elite-tactical-headset-desert-p-3511.html ( I've heard these might not be the greatest if you want to actually use it with a working radio. Cheap Speaker and mic.)
PTT -
http://www.ebairsoft.com/element-military-standard-plug-version-p-2593.html (you can configure the plug to match an existing radio if you want to try using the radio.)
Or you could spend more for ComTech II replicas.
http://www.ebairsoft.com/ztactical-comt-headset-z041-military-standard-plug-p-2604.html ( I don't know how well these work but they definitely fit the realism look you are going for.)
As people continue to grow in airsoft, hopefully they will find that a radio and headset are basic equipment. Even though people may not find the need to say much, it is vital so you can receive important information from your command or squad leader, allowing you and your team to make timely and coordinated efforts towards your objective. In some AO's due to the terrain and the vast area of play, it's also part of your safety kit incase you get lost or god forbid have an emergency. I could go on and on why a radio and headset should be standard equipment but the choice is up to the individual. If you want something usable and reliable, I'm sure others will chime in. I have had long standing success with my Cavalvy Elite II Headset, with only one minor gripe. If you want to know more about my experience with my headset let me know.