We're working on an approach where we are using the same landing page/form for all of our channels of a multi-channel program. And then based on a "Channel ID" querystring (that gets populated in a hidden "current lead source" field, we can route activity (campaign flows) into channel-specific programs. So basically, a master/parent program that contains all of the local assets (emails, landing pages, etc.) and then individual channel programs that just contain the campaign flows to properly assign program membership for the related activity.