Upgrade Ships to Other Blueprints

When upgrading a ship, instead of only upgrading to the most recent version of the ship's original blueprint, allow switching to a different blueprint (of the same hull type).

For instance, suppose I want to create a mixed-arms fleet, so I create one design for a Beam Cruiser and another design for a Missile Cruiser, and build some of each.  Later on, I decide I would be better off using only beam ships, so I want to retrofit my Missile Cruisers to use beams.  Currently, I can modify my "Missile Cruiser" design to have beams instead of missiles and then upgrade my Missile Cruisers to the new design, but that's a lot of extra work when I've already got a perfectly good Beam Cruiser template in my lineup, and it means the ships will forever be tagged as "Missile Cruiser 2" even though they now have beam weapons.

Instead, just let me "upgrade" them into the existing Beam Cruiser design (for the same cost as if I redesigned my Missile Cruisers to use beams).

NOTE:  This is NOT a tricky way of asking for the ability to upgrade ships that currently can't be upgraded (anyone who wants that can submit it as a separate idea).  I just want a more convenient way of handling upgrades that are already possible-but-awkward.