safe to overload objectSubId for a type?

Hi,

I don't mean "overload objectSubId" in any ObjectAddress that PG code
would ever see. I am only thinking of a data structure of my own that
is ObjectAddress-like and has all three components available all the
time, and for an object that's a type, I would find it handy to stash
a typmod there, and not have to carry those around separately.

As far as I can tell, most objects (maybe all, except attributes
and attribute defaults?) have the objectSubId unused. But I would not
want to paint myself into a corner if anyone anticipates making
objectSubId mean something for type objects somewhere down the road.

Thanks,
-Chap