Re: Easement to Access Lanclocked Property
whatever is granted in the documents creating the easement are all the dominant tenant has a right to. They may or may not have any rights to improve the easement beyond basic maintenance.
In fact, using the easement for more than the one house may not even be allowed. If the original grantor did not intend it to be used for multiple homes, its use is limited to a single home. Anything else would be over-burdening the easement.
The concrete driveway encroaching issue: unless the dominant tenant was given exclusive use of the easement or the concrete somehow impedes the dominant tenant from using the easement as intended, it is a non-issue.
If zoning ordinances do not allow the use of the easement for multiple homes or whatever other reason you say it would be in violation of zoning ordinances, it simply cannot be used for that purpose without a variance from the zoning commission.
I am not an attorney and any advice is not to be construed as legal advice. You might even want to ignore my advice. Actually, there are plenty of real attorneys that you might want to ignore as well.