You can pick whatever you want - reports in that matter wont do anything.
Why do I know this ? I got about 1k AP Shaco games - I won arround 50-55% of those but I'm sure I got atleast one report in almost every game I lost with him (because obviously every lose is just because of the off meta pick, that's the only option).
So let's say I got arround 400 reported games just for playing an off meta pick - I never got a warning or anything similar.
[Not to mention that I usually play off meta, so yeah]
However, if you got assigned to your role - beheave in your given role.
If you got support and pick, let's say Anivia (even though I don't know if that would go well), you have to play like a support. Help your adc to get fed, protect him and don't take his cs.
You can make many champs work as supporters, especially tanks and burst mages, however you should always ask yourself "Can this champion have a supportive value for my team or would another champion do better"
Some champions simply don't work as supporters - and at this point you're not being any help for your team and they have the full right to be mad at you.