I looked at the post for the halo mod and I wanted to inject somemore information about the halo fleets and give some screen shots to show you guys some of the ships. If your a good modder please make a halo mod itll be very very popular.
first things first you need frigates most of you have never seen a covenant frigate before so here it is in all its puny glory this thing is small has 2 plasma cannons and that about rounds it up Lol.

Now the Human frigate smaller but more powerful then the covenant version it is armed with about 4 archer missle pods on each side each with 30 archer missles in each pod and its most powerful weapon a small MAC cannon. (magnetic accelerator cannon) sounds cool lol. and about 4 shiva 30 megaton thermonuclear warheads.

Now there are more ships which can be used as the other frigates ( theres no pictures of them available sorry) They have the prowler which is the smallest ship it is armed with 14 hornet missles and 2 pulse lasers. Then we have Corvettes smaller then frigates but bigger then prowlers. Theres no info on armament but id say there are about 20 to 28 hornet missles and 4 pusle lasers. We also have a covenant destroyer and covenant frigates. The destroyers armed with about 3 plasma turrets and 2 plasma torpedo tubes. The frigates I have no idea there barely any info on those.If your gonna make it use your imagination.
Now on to Cruisers
The Human cruisers first most of these ships resemble the TEC Akkan ship.
We all remember the pillar of autumn This was a Halycon class cruiser The halycon Has Much heavier armor then any other cruiser with the price of weaker weapons. It is armed with a MAC cannon 4 shiva 40 megaton nuclear war heads 8 archer missle pods missles in each. and 2 50 mm point defense guns. it can hold 7 longsword squadrons i would say about 3 squadrons in game.

and we also have the Marathon class cruiser weaker hull then the pillar of autumn but more weapons. this is also a faster ship it has 8 as it says OVERSIZED archer missle pods about 50 in each. Can carry 6 shiva 40 megaton nuclear missles and has point defense guns All over its self.
see image here sorry image wont work http://halo.wikia.com/wiki/Image:Marathon-class_Cruiser.JPG
Then we have the normal Cruiser which there is no immage it has 6 archer missle pods can carrys 4 shiva nuclear missles point defense guns. it look nearly the same.
We also have Carriers from halo which could be for capital ships there is not image but i would image A much bigger version of the cruisers a wider side. the carriers have a large MAC cannon. archer missle pods and an unknown amount of shiva nuclear missle pods barely any info on the carrier. But it also says the can carry A lot of squadrons i would say about 6 in game.
Now they also have a SUPERCARRIER sadly in halo it was eliminated with most of the carriers. This thing would be bigger then the carrier and it would have A very very large amount of hit points. It says 10 mm of titanium a battle armor. it has a magnetic accelerator cannon i would image more missle pods and nuclearwar heads then the carriers. It can also carry a lot of squadrons.
One more Ship for the UNSC I couldent belive my eyes when I read about it it was called A COLONY SHIP!
now this REALLY REALLY BIG it is armed with a large magnetic accelerator cannon. Many archer missle pods many nuclear war heads and i would say in game 10 to 15 squadrons. this thing is behemoth.im very sorry for a smaller picture none would fit
if you want to see details look at this link http://halo.wikia.com/wiki/Phoenix-class_Colony_Ship double click the image to see it larger.

Now onto the Covenant ships 
covenant cruisers not frigates are the bulk of thier fleet frigates are rarely seen. They have a covenant light cruiser NO info unfourtunately I think it would be the smallest of Cruisers. we have the normal cruiser no picture armed with 5 plasma turrets and all on the lateral side of the ship pulse lasers. now we have a CSS class BATTLECRUISER armed with plasma turrets pulse lasers and plasma torpedos and energy projectors 1 one of them.it can also carry a squadron or 2. Here is what it looks like
check this link for information I used other links also but this one has best pictures http://halo.wikia.com/wiki/CCS-class_Battlecruiser
now onto the Covenant battleship =0 this one pretty cool sadly there are no pictures but it is armed with the most powerful weapons in the covenant ship arsenal 15 energy projectors and it has 4 plasma torpedo tubes and 6 plasma turrets. It can carry a squadron or and look like a larger version more bulky on the back end Of the CSS class battle cruiser.
Now onto the Reverance class cruiser this has 2 energy projectors and 6 plasma torpedo tubes can carry about 3 squadrons I would say. It says more of a small transport ship but there are no soldiers and troops in this game. There is also no picture i would image a larger version of the Frigate the first image on top of post.
This one sounds really cool and is typicly a very heavily armord ship. the covenant super cruiser armed with 5 energy projectors plasma turrets and pusle lasers. A larger verion of the battleship. no image 
now we have the Carrier class no image again sigh It has 5 pulse lasers and can carry id say about 4 squadrons. not to juicy of a ship.
Then the super carrier larger image of the carrier you get it.
The assult carrier used in halo 2 and halo 3 you saw them invade earth twice. They would proably be good at planetary bombardment and colonization. with an armanment of plasma turrets energy projectors and plasma torpedos. carry id say 2 to 3 squadrons. heres the image link sorry image to big to post here
http://halo.wikia.com/wiki/Covenant_Assault_Carrier i would imagine that the other carriers are just smaller verions of this one remember modders This thing is large.
so you can see size difference here this link should work http://images.google.com/imgres?imgurl=http://lh3.google.com/_O4EM5b61vNY/RyTqdfNd_dI/AAAAAAAAALI/pgcjYTpppoE/s800/CapitalShips-scale.gif&imgrefurl=http://picasaweb.google.com/lh/photo/XNo4H6raAZDjvvNHbJA3NA&h=458&w=800&sz=81&hl=en&start=3&um=1&tbnid=SgWHNzvOAG_3gM:&tbnh=82&tbnw=143&prev=/images%3Fq%3Dhalo%2Bships%26um%3D1%26hl%3Den shows image diagram
here are some more images of covenant ships at this link http://nikon.bungie.org/misc/sloftus_covenantcruiser/
here is where i got a lot of info on covenant http://halo.wikia.com/wiki/Covenant
here is where i got info on humans http://halo.wikia.com/wiki/UNSC_Navy
and a couple more things i was thinking we add things like The orbital defense stations for the humans

Maybe as a new planet type A halo ring we all know what that looks like
and the covenant high charity floating city/ planet

And that about rounds it up please post about all your ideas and what you think MODDERS PLEASE CONSIDER A HALO mod it will be awesome.