How about a profession where you can take on 2 other secondary professions? There would have to be restrictions on this. For example, you only have access to 4 skills during quests/missions instead of 8 skills.
Ninja or Assasin mentionned above should be able to stealth themselves.
The builder profession mentionned above seems like an interesting idea. It would be a great support profession.
Future Profession Ideas
spikydude