I hope you find a way to make this work.
- m:Transcom set up m:Translation teams several years ago; I think they've never worked but old members might have some suggestions (probably not?).
- Mentoring team members is needed, but I hope it will be sustainable in the long run. Probably using another mailing list would be bad: very specific high-traffic things can be discussed on some wiki page or bug or whatever, but keeping all this on the same mailing list seems better not only because more lists are harder to manage and weaker, but also because people not directly involved can still lurk and learn.
- Not everyone needs to know everything, for instance a language geek which knows nothing about wikis' inner workings and bugzilla could still be very helpful on CLDR and viceversa. Those skills (unless at a really basic level) are indeed required, but at the level of a[n effective] language team, not from each member.
- What teams lacked most was, I think, a list of actionable tasks/checklists they could work on. This is true of many features which are available but not used, think e.g. of the linktrail which almost nobody customises because it's not not documented anywhere (silly example). This connects to the Localisation and localisation portal restructuring, see also etherpad:l10n-wiki.