I am an avid player and admirer of Tribes 1 and 2. The only reason I liked Tribes Vengeance was the single player campaign. I loved it!
So, I came up with some principles, if followed, will make your game a winner to those that play it.
1. Give the choice of a wide variety of equipment to the player but limit the slots that equipment can occupy. This will force the player to choose wisely for the mission or how best to support the team.
2. Every piece of equipment, weapon, pack or base asset should have a counter. What do I mean? Well, if someone is bombarding your base from 500 meters with mortars, get out a sniper rifle and snipe that bomber from long range. Either that, or sneak up and take that bomber out with a special weapon that does one shot kills if done in a certain way (shocklance). Balance is the key to ANY game. Rule of thumb: If gamers are complaining too much about a certain weapon, chances are that weapon was improperly designed and probably needs to be omitted from the game. Weapons do NOT make the game. The way players use those weapons to accomplish a mission is. Always have a drawback for every strength a weapon possesses. If you have a gun that shoots a 1,000 damage in a straight line, have it go 10,000 kph, with infinite range, infinite magazine size with a 50m blast radius, it will ruin the game. You get the point.
3. Health of every player should always be a constant number. I like the number 100 because it represents a raw percentage of the player's health. Factors that prevent health decrease, limit health decreasing, increase health over time or immediately create interesting weapons, defenses and equipment. Even having heavy armor where either a certain amount of damage must be applied before the player inside it is effected. Those who choose a lighter suit of armor may choose a stealthy ninja-like setup where damage is increased if hit ... the key word is hit since that player can go visually invisible and that is his defense. Maybe your player wishes to be struck so the repulsor pack can be activated - pushing them away or activating the EMP pulse. I dunno.
4. Consumed, regenerative personal resource should also always be a constant number. The rate at which this amount is decreased or increased to the maximum may differ and thereby putting the balancing issues on the equipment and not on the player (which is easier to fix).
5. Leave out regenerative health. This promotes running from fights that could create tension and excitement in the game without one running away, healing up, and then coming back for revenge with surprise on their side.
6. Weapons and equipment should have predictive qualities to them. Forethought and skill should be the key to any tactical application of force in a game. If you have players scoring victories with minimal effort, this punishes those who have applied themselves to learn the game and play it well. Automatic weapons should be used sparingly, if at all.
7. Make the playing area large and cut down on frivolous decorations that slow down framerate and do not support the tactics of gameplay. Put in elevators, turning platforms and even maybe trains or something that moves players around the map. These spots are good for ambushes too...
8. Vertical movement is a must! Give us the ability to fly, whether it be by jetpack, low gravity or even magic. As always, put limits on vertical movement but if flight is under 1000ms with full resources that allow flight, the game will still be a running game like Call of Duty or CS:GO.
9. When designing equipment, weapons and the like, be careful to give all weapons the same DPS. Why do I say this? You can tweak a weapon to do 300 damage, with 75-125 splash damage 3m away, but have it fire once every 500ms and have it stray from your aimed spot 10%-15% of the time. A flame gun could have a cone of low damaging fire of 10m and has a 75% of setting anything on fire with a damage over time of 5-10 damage per 1000ms. However, it overheats if not managed correctly and may even possibly explode if struck with enough damage (maybe use a shield pack with it to protect the weapon!).
Even the mighty Shocklance that scores an instant kill needs melee range and the opposing player will not simply turn their back for you to use it on them. maybe you guys could come up with weapons that would require a lot of skill to score a one-hit melee kill similar to the shocklance. I would be interested in what your design would be. My thought would maybe be an energy garrote that take 3 seconds to kill and in those three seconds the victim has a chance to escape somehow (EMP grenade that damages some of his gear?).
10. Consistency of equipment. When a player is defeated, the equipment they had on them should be the only items dropped. Maybe if you wanted to make the game a bit more difficult, make it that dropped items are destroyable - with the possibility of blast damage! Additionally, make ALL items that are deployable and destroyable.
11. Populate the large map. Large numbers of players able to play at once.
12. Offer the Client and the Server software to the customer so they can set up LAN party events.
13. Focus on map play architecture and leave the pretty to those who think that is important (it's not after about five minutes of play, trust me). Excess graphics may sell copies but it hampers video card's ability to handle large maps. I would rather have fps than pretty building I will look at once and then concentrate on taking their base or flag.
Bottom line, go into making this game so it's playable but with a team. Supporting other people in completing a goal is enjoyable and satisfying to say the least.
I really do miss the days of Tribes 2 and the 64 person games on HUGE playing areas.