It's a really fun mod! I like how chaotic it can get, especially with the right events. But I definitely have some issues with it.

If possible, there definitely needs to be some sort of 'safety' check on respawns. It's very, very possible to wind up respawning in a location that gets you near or actually immediately killed, sometimes back-to-back.The lives system can help mitigate the effects, but losing several in a row because the game dropped you right in the middle of the crowd several times is a problem.
That, or giving the player some way to determine their respawn location.

When claiming a reward, the selection likes to move on its own without input. I haven't mis-selected yet, but should check that.

Possibly put some additional heavy weapon spawns on the map by default, particularly anti-vehicle ones. Not too many, of course, but it's very easy to wind up in a situation where your only option for that is grenadespam.

The absurd weapon variety is cool, but there's definitely winners and losers in the arsenal (plasma launcher takes an eternity to charge and doesn't do much due to overly slow projectiles that don't seem to track, precision weapons still dominate, AR is still ineffective), and it makes finding ammo for a given weapon a nightmare. Which, having to change weapons out a lot can be fun! But sometimes I wound up running around desperately looking for anything to shoot with. Putting some covenant weapons by the blown-up phantom might help with that. Due to it being on the very open and large map that is Sandtrap, it might be a good idea to see how upping weapon ranges, accuracy, and projectile velocity (near) across the board for both allies and enemies works out.
The Magma Pistol doesn't always leave a firepatch when fully charged and it's unclear what might be stopping that.

This specifically might be difficulty based (I was on Heroic), but: Many vehicles feel too vulnerable and/or ineffective. Notably, I found the Cobra to not be capable of dealing with much of anything, even while shooting on the move. Charge up shot doesn't do enough damage to vehicles and has a really janky delay before it even starts charging, and the basic shots seem to tickle most infantry, and the firebomb Warthog didn't score a single kill due to AI incompetence on the turret. Jackrabbit with machinegun was by far the most effective of those I used.

Also difficulty based and probably has to do with base Halo 3 stuff: Allies who aren't the Cyclops tend to die shortly after the wave starts, though here they seem to be even more aggressive than normal H3 allies and tended to mash their faces against enemies (total disaster during the Brawler wave, or any time there's a Juggernaut!). Being able to get Heroes back up sometimes helps, though, so I'm glad to have semi-permanent allies like them.
Also, allies don't seem to fire some weapons if you give them that weapon. I noticed this with the sentinel laser (given to an elite) and mangler (given to a guy in clothes).

Otherwise, no crashes so far, no weird bugs, surprisingly not very janky (outside Cobra issues). Helmeted grunts feels weird, but it's easy enough to adapt to that. Enemies often feel a little overly durable, especially the Skitterers and Juggernauts. I can't tell if they have some sort of weakspot, but the former can take an extreme amount of damage for being fliers and the latter eats multiple Spartan Laser shots while seeming to come in pairs.

Overall really good work and I hope to see this mod's progress!