Plutonium

They only save in private/solo matches (so does your rank and perma-perks).

Tried improving the code, added ambient sound when powerup is active, and iprintin message about powerup being picked up and being ended. I also tried drawing a hud powerup icon but it doesn't work.
I also removed zombie blood code because it wasn't working.

#include maps\mp\_utility;
#include common_scripts\utility;
#include maps\mp\gametypes_zm\_hud_util;
#include maps\mp\gametypes_zm\_hud_message;

//important include
#include maps\mp\zombies\_zm_powerups;

init()
{
	level thread onPlayerConnect();
    precacheshader( "zom_icon_minigun" ); // tried precaching death machine icon for hud, didn't work for some reason
	include_zombie_powerup("unlimited_ammo");
	add_zombie_powerup("unlimited_ammo", "T6_WPN_AR_GALIL_WORLD", &"ZOMBIE_POWERUP_UNLIMITED_AMMO", ::func_should_always_drop, 0, 0, 0);
	powerup_set_can_pick_up_in_last_stand("unlimited_ammo", 1);
}

onPlayerConnect()
{
	for(;;)
	{
		level waittill("connected", player);
		player thread onPlayerSpawned();
	}
}

onPlayerSpawned()
{
	self endon("disconnect");
	level endon("game_ended");
	for(;;)
	{
		self waittill("spawned_player");
			//only run this when the host spawns in for the very first time
			if(!isDefined(level.unlimited_ammo_first_spawn))
			{
				wait 2;
				level._zombiemode_powerup_grab = ::custom_powerup_grab;
				level.unlimited_ammo_first_spawn = "fortnite!fortnite!!";
			}
			
	}
}

//fires when we grab any custom powerup
custom_powerup_grab(s_powerup, e_player)
{
	if (s_powerup.powerup_name == "unlimited_ammo")
		level thread unlimited_ammo_powerup(s_powerup, e_player);
	    
}

unlimited_ammo_powerup(m_powerup, e_player)
{
	foreach(player in level.players)
	{
		//if powerup is already on, turn it off
		player notify("end_unlimited_ammo");
        //decided to use stinger from when you get ray gun from box
		player playsound("mus_raygun_stinger");
		player thread turn_on_unlimited_ammo();
		player thread notify_unlimited_ammo_end();
		player thread sfx_inf_ammo();
                player thread ammo_hud_create();
		player iprintln("^2Bottomless Clip!");  
		wait 30;
		player iprintln("^1Bottomless Clip has ended!");
		player playsound("zmb_insta_kill_loop_off");

	}
	
}

sfx_inf_ammo()
{
    level endon("game_ended");
	self endon("disconnect");
	self endon("end_unlimited_ammo");
	inf_ammo_ent = spawn( "script_origin", ( 0, 0, 0 ) ); 
	inf_ammo_ent playloopsound( "zmb_insta_kill_loop" );
	wait 30;
	inf_ammo_ent stoploopsound();
	inf_ammo_ent destroy();

}
//my attempt at making a hud icon for it, as expected, it didn't work
ammo_hud_create()
{
	self.ammo_icon = newclienthudelem( self );
	self.ammo_icon.horzalign = "center";
	self.ammo_icon.vertalign = "middle";
	self.ammo_icon.x = -16;
	self.ammo_icon.y = 16;
	self.ammo_icon.alpha = 0;
	width = 64;
	height = 64;
	self.ammo_icon setshader( "zom_icon_minigun", width, height );	
        wait 30;
        self.ammo_icon destroy();
}

turn_on_unlimited_ammo()
{
	level endon("game_ended");
	self endon("disconnect");
	self endon("end_unlimited_ammo");	

    self setWeaponAmmoClip(self GetCurrentWeapon(), 150);
	
	for(;;)
	{
	    self waittill ("weapon_fired");
		//simply set the current mag to be full on a loop
		self setWeaponAmmoClip(self GetCurrentWeapon(), 150);
		wait .02;
	}
}

notify_unlimited_ammo_end()
{
	level endon("game_ended");
	self endon("disconnect");
	self endon("end_unlimited_ammo");
	//changed duration to 30 because why not 
	wait 30;
	self notify("end_unlimited_ammo");

}

Changing starting weapon is just literally one line

level.start_weapon = "fiveseven_zm"; //replace fiveseven_zm with any other weapon name

I fixed the error and code actually runs! The only problem that it actually doesn't give you the flopper for some reason.

#include maps/mp/zombies/_zm_perk_divetonuke;
#include maps/mp/zombies/_zm_pers_upgrades_functions;
#include maps/mp/zombies/_zm_magicbox;
#include maps/mp/zombies/_zm_perks;
#include maps/mp/zombies/_zm_weapons;
#include maps/mp/_visionset_mgr;
#include maps/mp/zombies/_zm_powerups;
#include maps/mp/gametypes_zm/_globallogic_score;
#include maps/mp/zombies/_zm_score;
#include maps/mp/zombies/_zm_stats;
#include maps/mp/zombies/_zm_pers_upgrades;
#include maps/mp/zombies/_zm_utility;
#include maps/mp/_utility;
#include common_scripts/utility;
#include maps\mp\zombies\_zm_powerups;

init()
{
    checkthemap();
}

checkthemap()
{
    if( getdvar("mapname") == "zm_highrise" )
	{
    level.pers_upgrade_flopper = 1; 
    level.divetonuke_precache_override_func = divetonuke_precache_override_func;
    level.pers_flopper_divetonuke_func = pers_flopper_explode;
    level.pers_flopper_network_optimized = 1;
	}


}


divetonuke_precache_override_func()
{
	precacheshader( "specialty_divetonuke_zombies" );
	level._effect[ "divetonuke_light" ] = loadfx( "misc/fx_zombie_cola_dtap_on" );
}

pers_flopper_explode( attacker, origin )
{
	self endon( "disconnect" );
	radius = level.zombie_vars[ "zombie_perk_divetonuke_radius" ];
	min_damage = level.zombie_vars[ "zombie_perk_divetonuke_min_damage" ];
	max_damage = level.zombie_vars[ "zombie_perk_divetonuke_max_damage" ];
	if ( isDefined( level.pers_flopper_network_optimized ) && level.pers_flopper_network_optimized )
	{
		attacker thread pers_flopper_damage_network_optimized( origin, radius, max_damage, min_damage, "MOD_GRENADE_SPLASH" );
	}
	else
	{
		radiusdamage( origin, radius, max_damage, min_damage, attacker, "MOD_GRENADE_SPLASH" );
	}
	attacker setclientfield( "phd_flopper_effects", 1 );
	maps/mp/_visionset_mgr::vsmgr_activate( "visionset", "zm_perk_divetonuke", attacker );
	wait 1;
	maps/mp/_visionset_mgr::vsmgr_deactivate( "visionset", "zm_perk_divetonuke", attacker );
	attacker setclientfield( "phd_flopper_effects", 0 );
}

I don't even know if you actually can make PHD Flopper work on Die Rise, but still worth a try.

Alright so, I am a total noob to gsc scripting and I tried to enable flopper (persistent upgrade) for Die Rise.

As expected, I ran into an error:

1 script error(s):
 Unresolved external :  "maps/mp/zombies/_zm_pers_upgrades_functions" with 0 parameters in "_clientids" at lines 1,1 

Here's the code:

#include maps/mp/zombies/_zm_perk_divetonuke;
#include maps/mp/zombies/_zm_pers_upgrades_functions;

init()
{
level.pers_upgrade_flopper = 1; 
level.divetonuke_precache_override_func=::maps/mp/zombies/_zm_pers_upgrades_functions::divetonuke_precache_override_func;
level.pers_flopper_divetonuke_func = ::maps/mp/zombies/_zm_pers_upgrades_functions::pers_flopper_explode;
level.pers_flopper_network_optimized = 1;
}

Could someone help me please?

Hmm... maybe add death machine powerup?