Depending on how wild (or expensive) you'd want to get, you could look into a bale bed. Here in Kansas a lot of cattle farmers/ranchers have these on their trucks. The most expensive ones are designed to lift and carry two round bales of hay on the flat bed of a pickup...as well as allow you to unroll the hay to feed it. They also make pole hole diggers and various other "toys" to with it. The slightly less expensive ones only carry one bale. Some common brands are Bessler, and Hydra-bed. Here's a link (hope it works) to some photos of what I'm talking about...notice the 4 wheeler. http://www.triple-c-inc.com/Hydra%20Bed ... llery.html
They have a 2000# + lifting capacity, so picking up a bike wouldn't be an issue on the hydraulic cylinders. You'd have to fabricate some kind of sling or ramp to pick up your bike to put it on the porch, but it would certainly do the job. Somewhere on here (about a month or two ago) someone posted a video of some guys hauling snowmobiles on the roof of their skoolie. They had fabbed some sort of lift that was pretty cool, too. Hope this helps, or just adds fuel to the fire!!!