One of the reasons the MO3 loadscreens can look more polished is because the palettes require less distinct colors. Mixing in the other faction colors through the political map with the loadscreen might decarese the image quality.
This. Also most likely why the unit icons got axed from loading screens - they ate up precious color space from the limited 256 color palette.
I've been thinking about something. How come Ares can't do save games, but it can sync to a network, enabling online multiplayer? As far as I know, a netcode is much more difficult to do than saving, so much that some developers prefer to not have online multiplayer in their games at all. Unless, that's actually the secret of the project. How originally, most RA2 mods were multiplayer only, and such when the original team started Ares, they never even considered a mod having a singleplayer campaign.
Without knowing absolute specifics, I presume this is because of a fundamental difference in a process of saving a game and syncing info through a network. In former, you have to serialize all game data such as instances of various classes and their properties and the current values used for them into a format that can be stored on hard drive or an equivalent. If you expand upon the classes, which Ares has done to many of them, the old data serialization functionality will most likely omit everything new you added.
Not all of the information is required to be transferred via network events. For an example, only active properties of a vehicle unit like it's current HP, cell of residence etc. need to be synced, not the entire VehicleType class structure. The existing network events do the job here just fine (especially since some of the new features in Ares are actually built on top of existing ones, like AttachEffect stat modifiers actually use exact same properties as the crate stat boons), with Ares only adding few new ones for handling of game logic entirely absent from the game in first place such as Firestorm Wall.