Subdividing portion of park = loss of grandfathering?

So I have a duplex and apartment units on the far side of my park and hoped to subdivide them off and sell them. I’m on county land with no zoning and few regulations surrounded by the city but from what I’m being told if I lop off the duplex/apartments I will have to upgrade the park to current code (spacing, insanely wide roads etc.). In other words there is no “remainder” parcel, any subdivision creates all entirely new parcels that need to be up to current code. That likely kills the economic feasibility but it just seems odd that I’d lose my grandfathering simply because I’m cutting off a piece of the park. I know Frank and others have successfully navigated this process elsewhere, am I just a victim stupid local policy or is this fairly common? 

I ran into this same issue with a park I was preparing to buy about a year ago.  That park was going to lose it’s grandfathering and the park would not be compliant with current density requirements (homes per acre).  The city had a good relationship with a local surveyor and it looked like they were going to let it slide.  Unfortunately, they changed their mind once I paid the surveyor to begin drawing up the lines.  It killed the deal because the structures that I wanted the seller to keep were going to cost too much for the deal to work.  Unfortunately, you might be out of luck.

Depends on the local government and how bad they want change. I was offered this option with a park in a valuable industrial park area. The local gov wants nothing more than to tear my park down and have warehouses put in so they’d be willing to allow a minor site-plan revision to help me sell off portions to an industrial park developer.