Client Custom Fields in Custom Module

I have created some custom fields for clients that I want to use in my module.

I know that I can use $params["clientdetails"]["customfields1"] 2,3, and so on.

But if i later gives this module away/sell it etc. then I dont know if the custom fields would be 1,2,3, and so on in the other system.

Is there a way to get theese custom client fields without using this way. Im thinking something like

$params["clientdetails"]["customfields"] ["customfieldname"]

Where customfieldname is a custom client field.