Remove compasses from default inventory[U][B][/B][/U] and make it so you need to find compasses in chests
Fix Soups
~~Decrease the length of the rabbit stew~~ Completed
Add more materials in chests so players can craft more items, such as golden apples or arrows
Add a deathmatch if the first suggestion gets implemented
Lower rank boosters?
Allow spectating
Allow chests to restock after a long period of time
~~Not sure if it's just me, but fix the invis person glitch~~ Completed
Place enchantment tables sporadically across the map, and add EXP bottles to chests
Add a more variety of foods
~~Add boats, probably more useful for future maps~~ Completed
Instead of automatically teleporting a player to a game[U][B][/B][/U], make it so players can choose which game they join
Kits available[U][B][/B][/U] for everyone
~~Have a countdown for when game starts~~ Completed
Instead of Instant Health from mushroom stews, use Regeneration II for a few seconds. If a player has a lot of soups, this way they can't quickly regenerate health while they are under attack.
Add less powerful items at the chests at spawn, and make the loot better the farther away you get

EDIT: More suggestions -

Place items in random slots in a chest, in order for players to not be able to grab items easily and quickly
Increase the rarity of iron gear, diamonds, and iron tools
Add custom items that do special effects, to the user or to enemies (ie. more health, weakness, etc.)
Make some chests for fun to find, such as redstone traps, mazes, investigation, and parkour
Add buckets, cobwebs, snowballs, eggs, fishing rods, ender pearls, and tnt as find-able items in chests
Community map competitions?
Remove the grace period, now there is no risk to going to the center and getting armor/weapons first
If possible, add hostile spawn eggs that can't attack the player that spawned them
Just like the first suggestion, place the items in random slots, and only include parts of the iron set, and sometimes a diamond sword/axe/iron sword

That's all I can think of for now