Yeah, Cal is the reason why I think it can- and should- be done. Don't get me wrong, I love Cal as a character, but he's not the only one I want to see given the treatment. At the very least, do a generic Jedi 2 or 3 pack like they did back in the day. Hasbro did give us the Quantum Suits for Endgame that had a couple swappable heads in there, and were at least compatible with others too to make even more.
You'd think something akin to the Selfie Series would be doable- like a character customizer in a game, but in plastic form. Obviously there'd be limits, and people would need to be patient, but being able to pick through different heads, robes, sabers, hairstyles, scars, etc. Obviously limited to pre-existing sculpts and paint schemes, so you can't go too wild on things like eye placement or nose shape, but still. Want an orange Twi'lek Jedi? Go for it- the parts are more or less there. I'm sure there's some legalities in their contract that keep them from doing it, and I'm sure it's more costly than we fans think, but if there's any franchise to do it with that would theoretically be viable, it's Star Wars. Heck, have a window of time each year where orders are open, and they can spend the rest of the year making them or something, so it's not a constant open window and they risk getting swamped.
It just feels a little silly how good some of the fan-made options are, whether they're sculpted, 3D printed, whatever. I know Hasbro has to work under the confines of LucasFilm and Disney, and I can't really fault them there, but some of these fan offerings are so good, they're outdoing Hasbro!
But yeah, a build-up pack or weapons pack like we get with McFarlane, etc. seems like the first smartest option.