What about... not playing disguises in TES? Sounds stoopid.

I like this idea. Have some kind of emblem that you wear on your chest or around your neck that is an identification of faction, swap it out for whichever group you want to trick, how effective it is could be based on some skill and who you talk to.

The danger of being caught initially covered by sneak and smithing level (quality of forgery, from whichever forger). Speechcraft level check upon starting conversations with faction members. Harder checks depending on what rank or reputation member spots you.

Yep, that could be interesting.

[] All checks are passive, and done the first time a person from a cell sees you, or talks, depending on what you are doing.

[2]

• having to at least make an emblem before a disguise becomes effective ensures that disguises are not fool proof, as the alter ego could potentially rack up a sizable bounty.
  
• Unique marks should be expensive and time consuming (relatively) to avoid spamming different ones, forgeries are a close second in cost, depending on the quality
  
• switching one to another in front of a NPC opposed to either identity reputation in any way will leave the disguise useless (merged)