Just a quick guide to support tank Camille, a build which I've found to be quite effective. In summary, Camille as a support offers utility and CC just as good as many supports, while also being extremely mobile and doing surprising amounts of damage while built as a tank due to her percent health damage.

I'll list out the pros and cons for Camille as a support tank specifically, then you can decide for yourself :)
(Again, this is specifically in comparison to what you would expect from a tank support. So for example, even though she works well with tanky items, the fact she has no innate tank stats counts against her).

Pros:

• Decent CC and utility even for a support. Has very strong 90% AoE slow on W, AoE 1 sec stun on E, and of course her ultimate
• Exceptional *in-fight* mobility for a support - no traditional support really comes close. Movement speed steroid on Q, W can be cast while moving, and long range hook and dash on E (which is up every 6 secs or so by mid-late game with 40% CDR).
• Decent damage for a support, if built with some AS (and using the E AS steroid and Q resets). W does AoE percent health damage, Grasp of the Undying gives percent health damage. However, for a support her damage becomes crazy when you ult, you do percent health damage per attack. Note that her bonus damage applies WHENEVER she is inside the zone, not just to the original target.
• Excellent roamer (e.g. to mid) with ult and E stun + mobility. Not to mention the damage, especially earlier in the game.
• Pick potential with ultimate - point and click. Provided you can survive the enemy's burst (which you will be able to do as tank Camille, as opposed to normal Camille), your team should follow up and easily take down the enemy squishy.
• In built sustain with healing on W (which becomes ridiculous if you hit 3+ champs)
• 20% percent max health shield up every 10 secs late game (albeit only from one damage type)
• Fairly low mana costs

Cons:

• No innate tank stats/steroids (e.g. Alistar). This means Camille built this way will be very tanky, and definitely take a long time to kill, but will not compare to Poppy or Alistar, for example. (This is where you would use your mobility advantage).
• Mediocre peel - she can peel using the 90% W slow, the E stun, or her ultimate. These all have problems. The slow is only a slow despite being 90%, the E takes time to wind up (wall hook then dash) and only lasts for 1 second. Finally the ultimate doesn't instantly get the diver off your squishies, but on the other hand is very good for trapping mobile assassins (e.g. Zed, Leblanc). The peel certainly isn't bad, but doesn't compare to the instant peel of someone like Janna.
• No healing or shields for ADC - so you are likely to get outpoked in lane. However your W helps you through this phase by offering some counterpoke.
• Weaker lane phase - but not impossible. Reliant on jungler ganks (which you can set up).