A first person shooter jet pack game should have certain constants built in:
All energy is absorbed at a 1 damage per energy point. Maintaining the shield costs 1 suit active energy per seconds of operation. Maybe you change this to 15 seconds or even 5 second depending on how much endurance you want the shield pack to have. Maybe having the shield pack last for 20 seconds would make an light suit too powerful and imbalance the game.
This is why I like having fundamental constants:
Every power suit in the game is set at 100 energy
Every humanoid life-form in the game is set at 100 health.
Every humanoid life-form without a power suit has a walk speed set to 2 m/s.
Every humanoid life-form without a power suit has a running speed set to 5 m/s.
All suit jets use 1 energy per 1 second of operation.
Acceleration of the jet pack is set at 10000N*Second of thrust per 100 energy expended. Holding down the jet pack fire button, initiates an acceleration of (Thrust / Mass)m/s². A 200kg light suit would accelerate at 50m/s² burning the entire pack energy supply while a heavier 750kg heavy would accelerate at about 13m/s² after using up the whole 100 energy. An unprotected humanoid could wear a jet pack with no other equipment at have a mass of 120kg and therefore accelerate at about 83m/s² by using up the entire 100 energy. However, the acceleration forces would cause the pilot to pass out and maybe cause lethal collision or falling situations.
It takes a pilot to empty a jet pack of energy in under 5 seconds. The acceleration given by a jet pack is thus divided by five. If a jet pack has a acceleration of 50m/s² per 5 energy, at 4 seconds into the "burn", the player will be at 40m/s² (80% of 50m/s²). In 1 second, the player will be accelerating 10m/s², 1 second later, 20m/s², ect. One cannot just use up all 100 energy in the pack in one second. The rate of usage can be modified by laying off the jet fire button. Stutter firing the jets is more efficient.
Every power suit has a friction value of 1 when walking on solid ground or metal.
Every power suit has a friction value of 0.1 on solid ground when "skiing" when over a velocity/mass of 10m/s/Kg. A power suit, therefore, with a suit mass of 450kg (with pilot) would need to have a velocity of 45m/s before skiing. A lighter suit with a mass of 250kg (with pilot) would only need a velocity of 25m/s before starting to ski. Gravity manipulators and downward slopes can help reduce the initial speed requirement (because gravity is acceleration). The rational behind a need for initial velocity is that trying to create a very low friction on a solid surface would take a LOT of energy (more than the suit has) to constantly modify a large volume beneath it.
Every humanoid life-form is set at 95kg base weight (assuming clothing, suit inner liner, insignificant equipment, ect.).
Every humanoid life-form hit box is set to 2m in height and .5m wide.
Every humanoid life-form has a head sphere on top of a 1.75m x .5m hit box of .25m. Hitting this "head" does double damage to the health from piercing weapons (lasers, bullets, spears, arrows, ect.)
Every humanoid life-form occupies 100 liters of volume without the power suit.
Every humanoid life-form has a density of 0.95kg of mass per 1 liter of volume (allowing the individual to NOT sink while in a medium similar to water or sea water).
Every humanoid life-form outside of their power suit (which compensates for excess gravity and acceleration) in the game has acceleration (G) resistance set to +50m/s² before G-lock and negative acceleration of -30m/s² before G-lock. Therefore, the relation of a player to a gravity field, natural or artificial, can be tactically significant. If you want to get a better idea of this relationship of speed and time, go here: Acceleration Calculator.
Every suit has an acceleration compensator for dealing with positive and negative G's. It can be set to allow G-forces to be applied to the individual inside the suit before energy is used to counteract potentially harmful or even lethal amounts of acceleration. Damage can be applied to the suit normally but the blast is what is absorbed. Maybe have this set to +50m/s² and -30m/s² before energy is used to counteract acceleration forces. For every +25m/s² and -15m/s² in change it uses up 1 suit reserve energy (which regenerates VERY slowly).
For a comparison, TNT has an explosive velocity of almost 7,000m/s. Roughly translated to an 96kg individual unprotected by a power suit, that is about 75m/s² acceleration (for that one second only). The suit would absorb the 50m/s² leaving 20m/s² gravity to deal with. Maybe the player would use energy in accelerating in the direction of the explosion or "going with the flow" to reduce the acceleration effects. Your jets can accelerate your suit
Every suit is set to an energy regeneration of 1 energy per 1 second
Every pack that is set to a specific use (radar, stealth, shield, jammer) are all set to a usage rate of 1 energy drained for 1 second of operation. The effects are modified by this constant. No doubling or having the energy usage rate.