Here's something I've been thinking in my head since we have a similar issue. Could we make our channels/SFDC Types channels and assets. Making the Assets a parent campaign and the channels of deliverability the child campaigns. We could then see how the overall asset is preforming (and tie in any needed APIs) while allowing the child campaigns to get the influence and multi-touch reporting we want.
Cons might be that this makes the system much more complicated. Pros are this would meet both challenges head on. Are there specific reporting limitations with Full Circle, Marketo or SFDC if we do this? Is there something we aren't thinking about?