Unfortunately that requires a regular group, rather than the special identities.
Let's try this again. You need to create a stringtable.csv with the following:
Examples of use:
STR_CFG_PAPABEAR, CROSSUS ROADUS
STR_CFG_FIREFLYBASE, STEEL RAIN
And that's all you need to do. You can now enable chat from a unit that doesn't have to exist in the map, and his number isn't appended to the end of the identifier. It remains CROSSUS ROADUS instead of CROSSUS ROADUS 1. There are 4 identities you can set up, but you will end up with only two unique ones; one for FIREFLYBASE and one for PAPABEAR/BASE/HQ.
[west,"HQ"] sideChat "Hello from Crossus Roadus";
[west,"Airbase"] sideChat "Hello from Steel Rain";
Means that if you do something like:
[west,"Base"] sideChat "Hello from Crossus Roadus";
the identifier used will still show up as CROSSUS ROADUS even if it was only defined for HQ. So it's no sense in trying to use more than two.