Soooo... You'll be playing a ninja.
The anti-Operative backlash is a little tiresome. I think it's okay for someone to want to help the team in a way that doesn't involve being near any teammates. It won't be my class, but I think people who play operative because they want to be like Sam Fisher or Solid Snake aren't automatically deserving of ridicule. It's those who think they get to be the TF2 Spy and focus on backstabbing people that will be problematic.
I mean to be a medium Engineer. Essentially, I see the role and the body type as separate things, where body type is primarily about the way your character will fight, and role about the way you think of yourself in relation to your team. For combat, I like using an assault rifle, and I also like being mobile, so Medium is a good compromise. For teamwork, I like placing mines and sentries to control (to an extent) where the enemy goes, and I'll also like to be able to buff teammates' weapon damage.
I'll often switch to Medic, but seldom to Soldier or Operative unless necessary.