[TYPO3] Using $TCA to globally override sort and size of all FE Group select boxes?

[John Kallies]

My primary goal is to have all FE group select dropdowns in the Back End 
be a certain number rows, ordered by fe_group.title. I want a consistent 
appearance that fits a client's level of  FE group complexity (globally 
show more rows for a client with more FE groups, and just a few for a 
smaller client).

I've read through almost all postings with TCA in the title, and I've 
got the general gist of it, but I apparently am not connecting all the 
dots in my mind yet. I _do_ know how to edit the $TCA to change the size 
and the foreign_table_where in tbl_cms and for a given extension.

One critical problem I want to avoid is losing the overrides when I 
upgrade Typo3 source or an extension. I want/need to configure a global 
override for _all_ instances of an FE group select dropdown. An OK 
compromise would be to override all the $TCA for all extensions that use 
FE groups in one file and reference it in localconf.php's 
$typo_db_extTableDef_script. Ideally, I would prefer one global override.

I think I have all the right factors here, but I'm still not sure how to 
put it together, and I haven't seen any examples that try to solve my 
"global override" problem (none that I recognized at least).

Many thanks in advance,
John Kallies