Except for simply deleting them, of course.
There's so much room that can fit inside of 59 SP. 11 five-SP skills, 5 ten-SP skills, 2 twenty-SP skills, or 1 thirty-SP skills and some change.
But what'd I like most of all is to raise the max skill level of Jett's skills and giving them more passives/damage on skills.
The most obvious changes should go into Starline 4, and Strikeforce Showdown. Starline 4 does less damage than Starline 1, much like Starline 2 and 3, except would be a decent attacking skill on it's own. Starline 1, and possibly the other starline skills, happen to have a hidden final damage boost. Jett being a really unfinished class has several things missing about their skills, and some are wrong. Planet Buster actually has a cooldown around 5 seconds, rather 9 seconds displayed on it's description, for example.
Recommendation:
Starline 4 should gain a bonus 50% final damage to all mobility skills. Level 1 gives only 20% final damage, while increasing in increments of +1% final damage per level up to level 32 (max level 30 + paladin's Combat Orders). Jett's mobility skills include Starlines 3 & 4, Vortex Cross (includes passive versions from latter jobs), Vortex Jump, and Backup Beatdown.
Strikeforce Showdown is just bad for it's 1 SP consumption. There's only a 2% chance of activation and RNG in Maplestory is nothing but hell.
Recommendation:
Increase max skill level to 5 or 10, change the skill description from having a 2% activation rate to having a 5% or 10% activation rate; whenever the skill doesn't activate, gains an additional +5% chance of activating until it activates. Doesn't exceed 100% chance (derp).
Now after what I've discussed, Jett should still have 40-45 SP remaining.
10 SP should be used to increase the max skill level of Invincibility, giving it the stat boosts:
+15% damage, +45% HP, +30% defense, + 30 status resistance points, and +30% resistance to all elements. +1% damage, + 2% HP, + 1% defense, + 2 status resistance, and +2 resistance to element bonus with combat orders.
High Gravity should be increased to 30.
Max Skill Level: 20 ~>30
All stats: 20 ~> 30
Critical rate: 20 ~> 25
Stance: 50% ~> 70
Passive Boss Damage: 20% ~> 30%
Now with 20 remaining SP, Nexon can do 1 of 3 things: Add a new skill that has a max skill level of 20, boost 2 of these 3 skills: giga blaster, planet buster, or starfall by 10 points each, or add a new skill with a max level of 10 and boost 1 of the 3 skills mentioned previously by 10 points.
The only thing I see Jett lacking is the amount of base HP they have, which makes the huge % HP boosts they have from normal skills and Hypers become useless due to how low their Base HP is. Easily solvable, given the 20 SP remaining.
[New Skill] Stamina Stasis - Boosts Jett's vitality and raises his max HP. Max Level: 20
Level 1: +200 HP
Level 20: +4000 HP
I'm not even kidding about this one, Jett has 115% max HP from their own skills and hyper alone before including Kaiser's Link skill, Hyper Body, and Hyper AP. But it's so useless to have when you only have a base HP of around 10k and are already nearing level 200.