Regarding every "floor trap" idea: It would probably make sense if a player could only use 1 type at a time.
Shadow Cloak Spell - It covers you in a shadow for 20 seconds, hiding your player, with a ghostly shadowy blob in your place, making you unattackable and unable to attack and unclickable and unrendering you, but you cannot move away from the tile you are on or it stops. 2 minute cooldown. If your opponent has a Ring of Visibility or Ring of Shadows, they can see you but not target you.
Smoke Bombs - Credits to u/Beaverzzz for the original concept. You can deploy these at any time, and it creates a 3x3 space that lasts 20 seconds. Similarly to Shadow Cloak, it will "unrender" any player inside it and prevent you from attacking and being attacked. You can enter/exit it any time and jump in/out of it for "Winston shield" gameplay. You can only have one active at a time. 2 minute cooldown.
Requires 60 Ranged and 60 Thieving to use.
Callisto Soul Fragments - Spiritual Bear Traps - If your opponent enters the tile you placed this on, they deal 15 damage and cause a short 2-3 second bind (just like Callisto does). You are immune to your own trap. You can place these as much as you would mithril seeds.
There are no stat requirements to use at least 1.
Every 20 Hunter levels allows you to place 1 more bear trap at the same time up to 80 Hunter for 5 at once.
Abyssal Demon Cores - Teleport Trap - If your opponent steps on this, they are teleported to a random spot nearby, around 8 tiles, and it must be a location they could walk to. If they are teleblocked it won't work. You can only place one down at a time.
Requires 80 magic to use.
Standard Spell: Short Range Teleport - Allows you to teleport to a walkable tile within 6 tiles, and it works even while magically frozen. 5 minute cooldown, and is prevented by teleblock. I believe the Wise Old Man actually uses this spell.
Lunar Spell: Disruption Shield - From Pre-EoC. It's like Vengeance, but instead it nullifies the next hit you take. It only prevents damage, does not actually prevent freezes, but can counter a spec combo. 1 minute cooldown.
Arceuus Spell: Share Ailment - https://discord.com/channels/324132423636090880/1485660950915842048
Share Ailment is my #1 legitimate suggestion out of everything here.
In short, it copies your freeze timer onto your opponent. So if you get ice barraged, you can use this to duplicate the freeze onto them. Now they cannot DD you or freeze log you.
It also copies poison, venom, burning, corruption, and magical stat debuffs.
40 second cooldown between uses, 2x the ice barrage timer.
Dwarven Caltrops - Credits to @latent trail. It is placed on the ground like a mithril seed. It damages everyone that enters the tile (even if repeatedly) for 10% of their remaining HP and lasts 20 seconds.
Requires a Dwarven quest to gain access to use, with a level 65 smithing requirement.
Elven Stick Traps - Learn it from the elves of Prifddinas. You can place some sticks on the floor, which when stepped on by an opponent, do the Tom & Jerry "rake handle stick slaps you in the face" gag, for some decent damage, also it pushes you off the tile you tried to walk onto.
Requires completion of Song of the Elves.