Basic modding ideas:
In a similar fashion than the Complex mod did more ships. But not just the same model with different weapon loud outs instead actual models.
We’ve got fighters, gunboats, corvettes, frigates, destroyers, Carriers, Cruisers, Battlecruisers, Dreadnoughts
Those marked are not in it just yet but would make for nice additions and mixes between the present ship classes. A gunboat would be a mix between fighter and corvette larger than any fighter but smaller than a corvette.
Battlecruisers would be an enhanced version of regular Cruisers more armored and giving slightly more damage. Dreadnoughts should be a first priority target they are 1.5 as strong as a regular Battlecruiser 2.0 as strong as a cruiser and slower. Not closely as strong as Sajuuk of course for balance reasons.
More mission maps in general. There are plenty of stories to tell within the Homeworld Universe.
Trade ships
Would travel between allied motherships and shipyards depending on where you sent em. When docked with their mothership your ally gains little ru when it returns to you the same goes for you.
Transport vessel + Personnel Transport
Instead of just transferring Ru and ships just like that to your allies you must build a Transport vessel first. Lets say the ship costs 500ru then you transfer that sum automatically to your ally once the ship docked with either a shipyard or the mothership.
To transfer ships you need to transfer personnel first so they can make usage of your ships. That would add a certain sum to your ally of allied pilot slots and then you can transfer em over till the amount has been exhausted. I believe in some vanilla HW2 mods a feature like that was already implemented.
New game modes
Convoy duty: There will be only little ru on the battlefield and in order to gain additional ru income periodically at a randomized time ally troop transports enter the field per hyperspace. On pre designated or random areas. You would then have to guard these as your opponent will try to kill these. Per script it would determine the position of your own vessels and the enemy vessels to find a far isolated region of space where the convoy could hyperspace in. The same thing happens to your enemy to be wary.
A similar game mode was already added in vanilla Hw2 but never finished.
King of the Hill: Defend a randomized number of ancient stations to gain points till your enemies runs out of their points. Similar to the game mode of Kharak of Desert.
Coop: Survive with your buddy against endless waves of new appearing enemies while also getting randomized sub quests in order to gain benefits from it. Unit reinforcements, new tech unlocks, specialized none build able ships enhanced sensor range etc. If failed your AI enemy may get bonuses instead. So far we’ve got this kind of game mode only in single player form in few mods hosted on steam.
Exploration mode: The FX team is developing something like that right now. It contains a map system where you can jump onto other maps per hyperspace on pre designated points. Then you can explore an entire galaxy and encounter npcs giving you missions or fighting you as well as many map specific units you can’t build yourself… To bad that the Chinese develop this. That means half the time we wont understand what’s going on. ^^