A multiplayer FPS based in the vein of strategic and stealth games.
Something with character/class/loadout setup as in-depth as a Dungeons and Dragons sheet, potentially even deeper. The field is level- everyone gets so many points, so many skills, all to spend on trying to make the perfect soldier. Everything can be changed in some way- how long you can sprint or how much faster sprinting makes you, for one small instance. Things do tie together- being smaller than average gives you less overall health and ability to use certain weapons, but increases speed and in some cases, stealth.
Now that you've got your physical character- sans armor, equipment, training, and weapons, mind you- it's time to set up for the different game modes. Some are simple enough- normal team deathmatches, etc. but there are specific modes that take advantage of complex character creation.
Legacy Mode- This is a co-op mode where completing objectives nets points to spend in character creation, effectively working as a campaign with the chance to level up a character.
Legacy Battle- Two Legacy teams face each other, and depending on their performances, can level up and get more points. This can also be done as a tournament setting, where everyone connects to the same lobby and forms their teams, players not actively fighting able to spectate or change non-concrete things about their character.
Fast Track Brawl- Similar to Legacy, however, a character follows a pre-made track from Lv.1 to a higher level, usually 20 or 40, gaining a level for every kill or every 2 past the half-way mark. Fitting the Legacy mode into a much shorter game.
Lucky Dip- Before the match starts, everything past basic character creation is randomized. Two variants- one that chooses things semilogically in an order (chooses things dependent on what is rolled) or 100% random (stealth class with an LMG, anyone?)
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If you're playing in a normal match, the next thing you'll do is choose what training you have. Using a given amount of "hours", you can purchase perk-like abilities for your character. Some have prerequisites- LMG handling might require a certain amount of strength, for instance. Once you've expended all of your Hours, you then get to start choosing equipment, armor, and weapons.
You'll be buying these items from a Budget. Some weapons are better than others, and they'll cost more. You can take the best weapon you can afford, if you feel like that's all you'll need- or you can take less powerful guns for more equipment, allowing for better versatility.
Let's assume that we've built a smaller, lighter, dexterity-centric character. Through training hours, we've created a soldier who is made for stealth and infiltration- taking skills to remain silent firstly, and following up with breaching and parkour talents. As far as weapons are involved, we'll be taking a weapons-light approach- only one, a Machine Pistol.
A silenced MP9 isn't going to cost us too much as far as budget goes- which is good, because we're going to be spending a lot of cash on better armor, taking a normal armor class and filling every mod slot with sound-dampening material (3 slots, so each one reduces sound by 33%. If you're still in hearing radius, the knife is already in your back). That's most of our money- at least half on armor alone.
Lastly, we do have enough cash for some equipment, though not enough to get anything really fancy. We'll settle with three less-than-lethal breaching charges, simply because we get three of them in one slot, instead of one or two. (High-Explosive and normal, respectively)
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While in-depth, I now have a character based entirely around subterfuge in a somewhat classic sense. Getting around the map better than anyone else and doing it silently, while spending money on armor to stay alive in a firefight. Hopefully I won't need it- the best-case scenario would be playing away from a team, clearing hallways and checking windowed rooms for enemy presence while I'd play along the ledges, ready to break in through the window and cause havoc as soon as the front door is blown off.