Existing interfaces are difficult to change, because it would make people modify code that they already consider "done". They hate that. Usually it's easier to suggest a new interface instead. Incidentally, this is why stuff becomes bloated over time.

I have no idea how this would be done for Java, but for C++ I believe you can just submit a paper describing what you want to change, and the ISO standards committee will take it under consideration.

For proprietary languages like Java, Oracle could easily release a document that outlines the change, plus update their own libraries with the change. Not counting the development involved in deciding what changes to make, it's petty cheep.

C and C++ are international treaties. To change those you need consensus in their respective ISO committees. As I understand it, there's a small fee for Oracle to send a voting member to ISO, but there are no other costs. The tricky part is convincing everyone else on the committee that it's a good idea.

And some languages don't have an owner or a treaty. Oracle could release a compiler/interpreter that uses an expanded form of these, but it would have no way to force that expansion on other vendors. It could try to get ANSI or other national bodies to publish a standard, and there are fees to do that.

The problem you are describing doesn't sound like you need to change the programming language at all.

Say you have an API called Fred and you want to extend it. Rather than changing Fred, you can create a new API called Bert which extends Fred, add the new stuff to Bert, and just use Bert.

You might need to do a bit of juggling to get existing code to use Bert instead of Fred, so you would need to allow for the man hours to do that, but it's going to be a simpler task than changing an existing language.

Then apply the formula above to get an estimated cost.

Or you can do what most professional marketers do. Think of a number, double it, add your phone number and print it on a rate card.