I've done this many times, and I still often change modules (mostly G5 engineered) on my ships, depending on the activity I intend to engage in. But - the possibilities are limited. You will never, with any combination of modules and engineering, make an FdL a great exploration ship. Not even from the Mamba cargo ship.Try engineering different combinations of modules with different blueprints and experimental effects. You will get far more variation than a simple body shape change can provide.
I am aware that we could successfully play this game with 15 ships instead of 37 (or 38 including the Cobra Mk IV), but isn't it better to have more choices? This game does not need more ships with the same or similar characteristics, but there is room for different ships. For example, huge class - Frigate, Destroyer, Cruiser, Battlecruiser, Battleship classes. And I don't mean FCs - these would be ships that you can control, that you can fly around, that are destructible, that have a docking bay for smaller ships and that have a hybrid FSD for micro-jumps within the star system. That's actually what I'd like the most - to have an option to bypass the most boring part of this game - which is Supercruise. Because regardless of all the ships, all the modules, all the engineering, your experience, ranks, Elite this, Elite that - you still can't do anything to significantly speed up that SC.
But well, that's another topic.
And not even 20 new ships would mean anything if there is no proper gameplay for them.
As neither the Titans, nor the Thargoid Barnacle Matrix sites, nor the ancient battleground in Wregoe mean anything to us at the moment because there is no gameplay around them.