Ooooh, this will be a fun topic!
Let's see:
Luma Shot variants:
-Offense focused version (Could be called "Luma Comet"): Sacrifices the ability to influence Luma's positioning on the field for a Luma Shot with much more damage and knockback, greater speed, as well as a bigger hitbox and better priority, but Luma will immediately return to Rosalina's side if the shot misses. Another twist could be that Lumas die if the hit connects. This will be good for people who would rather not split their attention and simply want to control Rosalina on her own, giving them an incredibly strong projectile for trading out the ability to control Luma more properly. The main reason people find her difficult to use is because Luma being there means the player's attention must be split. This simplifies her play style for those people by giving them a really strong projectile, but limiting Rosalina's strategic options.
-Defense focused version (Could be called "Luma Mine" or "Luma Trap"): Activating the move makes Luma stay in one spot for a few seconds and draws opponents in, doing some moderate multi-hit damage as Luma spins around in place. Rosalina is not effected and can use it as an escape tool. Activation is really quick, but Luma cannot be called back or further influenced until the move finishes, and the move has low priority, meaning Luma is open to being hit hard if the attack does not connect. This would still be a simple variation of Luma shot as the animation will be similar, the Luma simply spins in place.
Star Bits variants:
Simply make one version a thin, stronger, and long ranged stream with some knockback, and another that is very wide and does a lot of damage, but does not cause opponents to flinch.
Launch Star variants:
-Spring Star: Only goes straight up and makes her move pretty fast, but Rosalina will be able to damage and knockback anyone she hits. The damage dealt would be low and the knockback low, but there will be a gust of wind to push opponents away if they are near Rosalina at the VERY start of the move. However, it's more predictable due to only going in one direction, and leaves her floating slowly down due to her floatiness. The Launch Star model will be replaced with the Spring Star model from Super Mario Galaxy.
-Launch Star Cannon: Rosalina will hover inside the Launch Star and an aiming reticle will appear. You can shoot Rosalina in any direction, but you have to charge it. The lowest charge launches her half as far as the default version, but the highest charge launches her 1.5 times as far as the default version. The move deals damage and knockback according to the charge level. Highest charge is a K.O move if it connects with people at decently high percentages.
Gravitational Pull variants:
-Gravitational Shield: The items and projectiles caught will orbit around Rosalina, similarly to Mega Man's Leaf Shield. They can block projectiles as a result. However, Rosalina cannot use the items, but other people can steal them. Also, if any of the items orbiting her are explosives, they will blow up in Rosalina's face if shot or if any of Rosalina's own moves connect with them, and could obviously K.O her if she's at a high percent. Rosalina can deactivate the shield after a few seconds (this restriction is in place to punish you if you happen to catch explosives as part of your shield - also, should your shield contain items, they will simply drop and other players can use them. Projectiles like Aura Sphere will simply disappear). Also, you cannot build up your shield over time, if you want to create a new shield, you have to get rid of the shield you have. So you want to catch as many projectiles and items as you can all at once.
-Gravitational Push: Pushes back projectiles, items, and opponents. Does a small bit of damage to opponents. It trips up grounded opponents, and sends aerial opponents into a helpless, tumbling state. Items will not get neutralised though, meaning you cannot use them - if someone throws a Pokéball at you, for example, and you use this move, it will prevent it from hitting you, but the Pokéball will still aid your opponent.