How about adding some sort of invisibility drop suit module? It could perhaps act like an active vehicle module that needs to be activated and has a certain time limit it operates for and a certain cooldown rate before it can be used again. Just to keep it balanced, perhaps it will have to 'soften' armor. In other words, reduce HP of the user's armor by a certain percent that gets higher (actually, lower mathematically speaking because it reaches a higher negative [-]) the more advanced the module is. I am not talking about profile dampeners, I'm speaking of actually being physically invisible. There already an invisible affect as soon as you spawn, but it goes away after a certain time limit, or when you move. Making this affect manual at the cost of armor HP would be ideal for reconnaissance-like strategies, like going behind enemy lines safely and hacking objectives behind them. Speaking of objectives, perhaps the user would have to deactivate the module in order to hack objectives (that way, they wouldn't be impossible to kill while they were hacking the objective ).

Cloaking is planned, confirmed by CCP http://dust514.com/news/blog/2013/03/equipment-is-your-friend/

I see what you are sking about this, invisibility would be cool. but on the flip side, there will be teams of scout shotgunners running up behind our team mates and slaughtering them. Invisibility just wouldnt work. unless it was only on for ten seconds with 30 second cooldown or something along those lines.