I have the same challenge in a different context. I guess you need a reference to your SAAS identity in every entity, in order to make sure that your user only sees records from his own SAAS identity, and not eg the quotes of other SAAS companies.
Did you consider to make your own incremental number logic in a microflow, using this SAAS identity link in combination with a lastNr field on with your SAAS identity object?
when creating (or better saving) a new record, it looks the lastnr for this SAAS identity, adds 1, and updates the lastNr info.
I usually prefer random IDs (see community commons randomGUID function) above (scoped) (auto)numbers. Easier to maintain and more reliable if concurrent writes / creates can occur.