Promoting & Merging Heroes Mechanics Question

So, from what I know, when you merge a hero, the skills and everything inherited and SP of the one you are merging in are transferred to the new one. For example, if you merge a fully built 5-Star Cherche into a new base kit 5-Star Cherche (for the sake of better IVs), the new base kit one would have all the skills learned from the old one.

This is correct, right?

So then in that logic, if you know you're definitely working towards a unit, is it a decent idea to start building it on a lower-IV version and then just merge it later? Sure it'd require leveling up again, but that's good for SP anyways.