It’s a fact that no one uses optical drives anymore and so why not replace the one in your late-model MBP with something a bit more useful like an SSD. It doesn’t really seem that hard as long you’re comfortable totally disemboweling your MacBook Pro. The SSD and optical drive both use SATA so it’s really plug and play and only requires a special adapter plate to properly hold the SSD in place.
It’s really up to you whether you use this speedy new drive as your primary (that’s what I would do) or as a secondary drive. You can always decide that after all the real fun is done and the mac is back in its original assembled state.