Hi hugone, if you think snapshot "from User Media, Canvas Snapshot or DrawingCanvas-save image" is causing problems for you, I dont think I can help you with that.
User Media in an iframe is not supported in all platforms as you suggested.
I will still use the original UserMedia plugin from C3.
I wont be making a new plugin for UserMedia, as developing that will require creating dependencies for support in other platforms. And afterall, I would end up developing a similar plugin like the original ones.
Your request is too much customized and I would suggest you to try to do it yourself.
Or you can ask the developers of C3 for more insight into this problem.