It may not be as simple as some people seem to always assume the things they want are.
This may be a useful idea for newer players, but eventually, what Lestat suggested is a better solution and in no way ridiculous. Personally, I'm more a fan of using different types of ships for different roles, but have finally found a ship that (for me) is the best option for a few different roles, and having more than one is a far better option than storing loads of engineered modules and swapping them out - with or without a quick profile system. There are only two modules that are duplicates between my combat and mining builds - thrusters and FSD. Every other core module, optional internal, utility, weapon and even armour is either a different module or engineered differently. Once you get to that horrible place where you have 50-80 different engineered weapons (stupid PP Weapons!) there simply isn't enough storage space to accommodate multiple ship loadouts, so a different ship does become a better option.
You've made a reasonable case as to why you personally wouldn't really need such an option with the way you currently play, though at the same time, it still would have been cheaper and less work for you to do the same thing with saved loadout profiles. In any case, that doesn't preclude other people sharing more modules and hardpoints across their builds, as well as having more builds than you, and thereby benefiting more from saved loadout profiles. Obviously, module storage capacity would have to be increased along with this feature, as well as improving module sorting and grouping.
If I have just two Anaconda builds which both use 6A G5 FSD, 5D G5 (Lightweight) Life support, 8D G5 (Lightweight) Sensors, 7A G5 Thrusters, 6A G5 Shields, and 2x 0A G5 Shield boosters, all of which would be fairly common across builds, then to have to purchase and engineer each one twice, as well as purchase another Anaconda, when I could just click once to switch loadouts, is indeed a ridiculous prospect. And that's just two builds.
As for how simple it would be, as feature implementations go, this would be one of the simpler ones. It requires no new assets, and basically amounts to some logic to check inventory and replace location values. I could do that in a day or two on my own, including preliminary testing.