hii @brianteeman
i see two approaches basically for this fix:

One, is to create a new file tpl_cassiopeia_extended.sys.ini: simple and isolated like the parent cassiopeia has its own such file but the problem is it will require duplicating position strings for translators

Second,If a child template doesn't define its own position translation, fall back to checking the parent template's keys (TPL_POSITION*). This resolves it for cassiopeia_extended and also covers any current or future child templates without needing duplicate files or translations.

but this second approach would require change in core php module

i think second approach is better though its bit longer approach would love to hear your all feedback