How to delete a plugin in the best possible way?

We have developed plugin “Smart Manager” which on extract gives for eg: smart-manager1 for lite. Now, for pro we give smart-manager2 which is sent through mail. Till now our users used to manually delete the lite version & add the pro one.We, have planned to make follow common directory only i.e smart-manager1.So, our pro users would be having smart-manager2 after our new release they would be getting the new smart-manager1.So, when they download the new release we want to delete the smart-manager2 directory.But, while deleting the plugin it asks for ftp details.So, now our problem is what if ftp module is not installed on the client side.So, how to handel this? Have anyone come across it & have idea for it?