US International Keyboard - Microsoft Style

I have seen a number of posts that raise the exact same problem as I am encountering. The problem is very simple:

A large number of us are migrating from MS Windows. We work in multiple languages (in my case, English, French, and Portuguese). We use a standard US keyboard as our input device. Microsoft has implemented a 'US International Keyboard' that works as follows:

~ + letter will put a tilde (as in õ, Ñ)
' (apostophe) + a vowel will put an accent on the vowel (as in à, È)
' (apostophe) + a vowel will put an accent on the vowel (as in á, É)
' (apostrophe) + a 'c' will create a c with a cedilla (as in ç or Ç)

The current US International keyboard with deadkeys, as implemented in ubuntu, comes very close. The current implementation of apostrophe and c produces ć. The only problem is the challenge of producing the ç. In the current implementation, this is accomplished by using the Right-Alt key plus the comma. On my keyboard (as in most US standard keyboards), the comma is directly above the Right-alt key.

We are asking for an option that will allow the apostrophe + c to be used to type the ç. This is a problem for many people, particularly for those of us who work on microsoft during the day and ubuntu in the evening.

I suspect that you would get a HUGE thank you from the community if you can make this happen. I am a newbie, but if developing a new keyboard layout based on an existing is simple, then I would be happy to contribute to that.

Many thanks