Hi y'all, I just recently signed on after seeing TheDog's post on reddit and thinking maybe I could be of some assistance. I have never done game scripting before, but I have programming experience, and I am fixing to have a lot of time on my hands. Y'all seem to be focusing on building assets at this time, so hopefully by the time for coding arrives, I'll be able to be helpful.

Anyhow, I noticed there doesn't seem to be any clear goal to work towards and I think it's really important to have an objective to work towards. Obviously, eventually we'd want a custom map, lots of assets for people to use, multiple scenarios, and maybe even a single player and/or coop campaign. But as a more intermediate goal, something that could be used as a first public release, I propose multiplayer scenario similiar to insurgency. Basically, the UNSC would have a single ground base as well as the frigate serving as spawns. The Insurrectionists would have between 10-15 hidden camps scattered around the map that could be spawned at and are guarded by AI, as well 3-5 heavy non-respawning anti-air vehicles capable of bringing down the frigate, which would be there primary objective. The AA would have long range (about 20km to prevent UNSC from hiding in the corners to avoid defeat) but relatively slow firing and with limited ammo to encourage shoot-and-scoot and resupply at camps and it would require around 40-60 hits to bring down the frigate. The UNSC would have to kill all the AA or destroy camps to win. Even if the frigate is brought down the game wouldn't end(unless it is brought down over water, further encouraging staying on the map), it would enter a permadeath mode, with the Innies trying to enter and blow up the frigate's core and UNSC have to rush to defend it. Either side would win by wiping each other out or the Innies by blowing up the frigate. This scenario would be something new for the community, showcase all the equipment, weapon, and vehicle assets and some of the structural elements could use in the base and camps, but at least initially it could use the default arma map. I think is a good starting objective anyhow. Below I have a list of personel, weapon, and vehicle assets that I found on the wiki that are for the most part from the Insurrectionist era:
Personel
UNSC:
*Marines
*ODST
*Pilots
*Navy Crew
*Spartan I- there isn't to much on their equipment but they fit the period and aren't as overpowered as the IIs
*Spartan II- obviously a lot to work from, but it might be too difficult to model the power of the MJOLNIR armor and if is it accurate it might be a little op

Insurrection:
*Innies-FIA with Halo weapons
*Commando-would have some captured UNSC and police gear
*Terrorist-civilian garbed, suicide bombers and IEDs were used, including in civilian areas
* Defector [halo.wikia.com]-basing them on UNSC Army makes them distinguishable, also more likely that they would be closer to the population than Navy and Marines

Weapons
UNSC:
* MA5B [halo.wikia.com]-assault rifle
* MA5K [halo.wikia.com]-carbine
* M739 [halo.wikia.com]-LMG
* M392 [halo.wikia.com]-DMR
* M90 [halo.wikia.com]-Shotgun, slightly out of period but iconic
* M6 [halo.wikia.com]- probably do both a scoped and unscoped variant
* SRS99 [halo.wikia.com]-sniper rifle
* M41 [halo.wikia.com]- rocket launcher, should be able to lock on to air targets to provide SAM capabilities.

Insurrection:
*MA3-no pictures, predecessor to MA5, maybe make it non-bullpup to make it look older
* HMG-38 [halo.wikia.com]-even older assault rifle
*M247- same gun mounted on warthogs but in LMG form, supposed to be only effective at short range
*DMT-law enforcement variant of M90, lacks pistol grip
*a single tubed variant of the M41 to provide anti vehicle support
*a hunting or police esque rifle to serve as a sniper
*Civilian M6-lacks explosive rounds so does less damage

Vehicles
UNSC:
* Warthog [url]- not sure how many of the variants y'all want to include but the LRV is a must*[url] Troophog [url]*[url] Cougar [url]-IFV*[url] Scorpion [halo.wikia.com]-again out of period but iconic
* Hornet [halo.wikia.com]-light attack and recon VTOL
* Pelican [halo.wikia.com]-transport
* Mongoose [halo.wikia.com]-ATV
* Fox Cannon [halo.wikia.com]-artillery

Insurrection/Civilian:
*Civilian Hog-there is mention of rebel plating them in armor to make a makeshift apc
*Civilian Pelican-also police variants
*Civilian Mongoose-not explicitly mentioned but seems reasonable
* Spade [halo.wikia.com]-good canidate for a technical
* Genet [halo.wikia.com]-standard police patrol vehicle and civilian sedan
* Uberchassis [halo.wikia.com]-Civilian luxury sedan
*LTUV-M-mentioned as predessor to the warhog, militarized SUV, of East Asian design
* Forklift [halo.wikia.com]
* Tractor Unit [halo.wikia.com]-ground transport
HC1500 [halo.wikia.com]- civilian transport, either this or the tractor with a M97 [halo.wikia.com]-mounted on the back could serve as the heavy AA

Hope the list helps. Tell me what y'all think of the scenario, and if y'all know of great guides of tutorials on scripting for Arma, that'd be great. Thanks.