I know a PE also, lol. But retired my license.
The barn was a kit from a local hardware store, although I designed and got my building permit before they gave me their plans. The roof trusses are stamped drawings by the supplier.
The problem with a lean to coming off the existing roof is it’s not designed for the load increase. It’s rather simple to come off the wall, but will have to calculate header because it now has to support half the lean to load.
The shed has to go somewhere to get the camper parked at the right of the barn. It’s not getting trashed unless it won’t move.
Metal carport for camper is another option I have thought of, thanks for the price.
Prices sure have gone up. My whole barn was around $11k not counting concrete.
A 6x6x16 now costs $72.