Not sure if it be possible in halo 2 but why not make a Ghost act like a paranormal ghost when boosting it can phase through other objects Npcs,Vehichles and some props

As for a sentinel beam weapon you should do two options a rainbow beam which allows for a rainbow sentinel to be apart of the funny roster

another option could be the Numa Numa Yay song machinima the longer you fire the louder the song gets and does more damage

Also amazing to see the mod fully public now was awesome to get to test it before full release

Holy hand grenade?

Miniature Scarab: fires flame beams that ignite targeted enemies (and vehicle moves at half the speed of a Scorpion). Allows 2 NPCs to ride on hull for support.

Rocket Jumper: Fires 0 damage rockets that have massive knockback (and makes the player less likely to die from fall damage).

Stick-and-rock-launching Sentinel Beam

Can you elaborate on the Stick-and-rock-launching sentinel beam?

I think it'd be cool to do something with the grunt funeral skull kinda like in the first cursed halo. When you kill grunts, they could explode into a bunch of rainbow grenades for some good chaos.

I have some oddball ideas to this:
-Wraith boost at Mach speed.
-Regret beatboxing with random gesture animations (native language) to his followers
-Holy Sentinel Beam: Send people to rapture from consecutive hits.
-Ghost has no collision to objects and players
-Scarab move in a fast pace.
-Jackal speak like a toxic CoD player (fitting for legendary)
-Hidden Scarab gun turn into Raid which kills insects intantly (when picked up, all enemies replace with drones in Metropolis).
-Regret's gaming chair (he can't fly but he can teleport).

Funny cutscene/in-game scenes:
-Cairo Station: Big fart echo from Athens and Malta. Jesus Christ flies over the Cairo Station.

-Outskirt: Chief is dead from the crash but wait, you're still here and Johnson is mourning for the whole minute (questioning if you're alive or not).

-Metropolis: Taking a pelican lead to a special place...

-The Arbiter; Grunt exploded from methane overload during the phantom cutscene.
Deja vu, you see another Arbiter along with the elites at the opposite side of the map and it is exactly like in the beginning. Killing the clone arbiter will kill the player.

-Delta Halo: Suddenly, you stumbled into the dark world with themes and everyone in some sections.

-Regret: Gondola/Elevator moves at an insane speed (Cortana is completely caught off guard).

-Sacred Icon: Marine radio comms are replaced with skittles addiction.

-Gravemind Arby and Chief were violently toyed with by the Gravemind. Chief is teleported upside down, again.

-Gravemind outro/High Charity intro: covenant band at the Mausoleum playing Breaking Benjamin (the music stops abruptly if attacked), Mercy is a bit freaky with the flood.

-Uprising : Intro: Arbiter doesn't stick the landing. Outro: Rtas accidentally fires the wraith at Arby before he reveal himself. Brute aren't good at driving the phantoms (ends up crashing)

-The Great Journey: human prisoners and Scarab are doing the Caramelldansen dance.