The poor design of Caroleans is because fitting them into the Swedish civ is like trying to fit a square peg into a round hole. To compensate for Sweden not having skirms or goons they were made into a do everything unit with excessive range and ranged multipliers. Those features run completely counter to how they actually fought and undermine them having a coherent design.
Their historical fighting style was to march forward and deliver a shot range volley before charging with swords and pikes. So if you want them to emulate their real life role they should be a fast, low range and high melee musketeer. Even the faster RoF kinda fits to represent the point blank volley before charging in.
To get rid of the features that undermine a realistic role for Caroleans, the initial shortcomings of the Swedish civ need to be addressed. Now that Sweden has an actual light cav unit the ranged cav multiplier doesn’t seem necessary at all. It has a secondary function of trying to force them to be paired with pikes to protect them from ranged cav, but that still doesn’t seem like enough to make the pairing viable. Their range could also be significantly and Sweden could have some kind of Arquebusier to properly fill the light infantry role (at least in the early ages).
A more realistically themed Carolean could look something like the following:
Giving ranged resistance instead of melee would compensate for shorter range. It would also reduce their effectiveness against melee cavalry. Resistance could flip to melee while the Carolean Charge ability is active.
The cavalry multiplier could be moved to melee to make it a more standard unit.
Siege attack could be lackluster (potentially even worse than I’ve shown) to give an opening for pairing with pikes. It also has a historical justification since the Caroleans suffered massive losses when they were lured into attacking Russian fortifications in the battle of Poltava.
For the Cards that currently affect them, they could be reworked as follows:
Snaplock: +1 range to Caroleans and Hakkas, and +2 range to Arquebusiers
Platoon Fire: +10% ranged attack, and faster RoF at close range (like Gascenya)
Svea Lifeguard: +15% hitpoints and +10% melee armour to Caroleans and Grenade Troopers