Hi Sanu,
In any kind of programming the use of methods to separate out your code logically and promote re-use is always a good thing. It's a good thing and defintely something I have done before.
If it makes more sense that these methods belong to a global object and could be re-used then make a global class and refer to the logic from your proxy.
Re-generating the code has no impact to the code of any of the methods. By this I mean that the code itself is never changed or deleted. It only affects the interface (importing params for an inbound proxy). So removing a field from an interface will affect any code that directly makes reference to it in the proxy class.
You should probably try it and see. It's a simple to test and will give you more confidence in making changes.
Cheers,
Katan