The workaround you are suggesting is what I’m actually using as told in the opener. 
I see your point, but I also think there’s no point in keeping the “bad” (take no offense pls…) implementation and let users still have it around longer than necessary, as this just makes a stronger leverage to procrastinate the fix. 
A way this could be fixed is to leave the actual icon as a “legacy” item, with a notification similar to the orphaned child when that item appears in the builder suggesting the user to switch to the correct one, which will just have a different classname. Make finally the legacy item appear in the builder only if it already is in the current template.
I don’t know it you have tracked this, but a very similar problem appears here: How to Hide Nav (Nestable) Items on Desktop but Reveal on Mobile, Without Leaving Column Gaps