PC laptop + VNC + Mac Mini server for iOS development. Is it practical?
Yes, VNC will give you access to the full Mac desktop and to Xcode for iOS SDK development, if the Mac is so configured.  Apple sells remote admin tools that use this protocol.

The problem with using VNC for iOS development is that you will also need access to the Mac's USB port to do any direct app loading and debugging on an iOS device.

If you can do without needing to connect a debugger, you can transfer Ad Hoc iOS app builds and provision files from the Mac to your PC and use iTunes to install your apps for testing.

If you want to try it out, there are reported to be services that will rent you VNC access to a Mac in a data center somewhere.  You will need admin/root access to install the iOS SDK tools.

If you prefer RDP to VNC, iRAPP is a commercial RDP terminal server available for use on Mac OS X.