Yes, using custom formats it should be possible (not only for .ics but also for vCard as well, I would imagine, because both are just text formats).
An aside:
Recently I have been looking into sharing vCards and, what I found is that Outlook does not accept Unicode vCards without the user making a setting inside Outlook (for the several versions we tested). So you are stuck getting people to do that, or, making two vCards - one for Windows and one for everyone else.
I mention this because, although I have not tested it, I bet ics files might have some similar constraints as to what works universally, or not. Just a heads up.