I've tried drafting a response to this several times over the past couple weeks or so since Danny's original inquiry though I've scrapped it all of those times.
Basically, I'm not sure how to give you a percentage of how done the mod is at the moment so instead I've decided to just elaborate to the best of my ability where each part of the project is currently at.
Level 1-3 Story Missions
Aside from Levels 2 and 3 needing various HUD icons to be made, the story missions for these levels are near-final.
Level 4 Story Missions
Level 4 Mission 1 was shown off in the trailer and for that we tried to make that mission as complete as possible but it is still going to see various changes before release. Besides needing more complete Hellfish mode support, the route used in the trailer was actually specially created just to utilize more complete areas of the map for the showcase. The original route traverses other zones of the map that were not very fleshed out at the time and will likely be restored for the release version.
As for Mission 2 onwards, development has begun and we've been talking through the ideas we have for the rest of the level to work out what is going to work and what needs to be refined or replaced for the actual implementation of the missions.
The Industrial Zone
At this point, I would estimate the map to be around 75-80% done. I might be being a bit conservative with that estimate though as things are moving along pretty quickly and it's really shaping up to be a great fleshed out level.
The first area of interest is the hideout Agent S mentions at the end of the trailer which at the time did not exist at all but is now nearly done. This is another new interior area which acts as Agent S' base of operations. It also includes the map's first fully original gag! On that note, I'm hoping we can match or exceed Radical's lowest gag count (6) with this level though the number of gags isn't final yet.
Next up, I've been working on filling out the last couple zones that are still kind of barebones with a variety of generic structures and notable landmarks. I've also been trying to incorporate more shortcuts into the map as well.
Lastly, Cola Boxes and Cola Machines have also started to pop up as it wouldn't really be a proper level without them.
Level 1's bonus mission is done and ready to go while Levels 2-4 have plans that are not yet implemented.
In Donut Mod 3, we replaced the "Street Race" moniker with the more generic title "Challenge Mission". This was done to reflect that this set of missions is more than simply various kinds of races. Instead each level had a destruction derby, a checkpoint race and 1 unique challenge.
Since then, we've discussed a lot of concepts for what these should be in Donut Mod 4. One idea we've been discussing in depth is giving each level its own "theme" of sorts, wherein all the missions in that level are hosted by a new set of characters and are themed around their association with the player character. We actually showcased one idea we had before with the Mob Heist mission in Level 1. That concept is still alive though it's likely going to be re-located to Level 2 in favor of something we feel is more suited to Homer.
Wager Race Replacement
George and I have been discussing and developing a new, more dynamic replacement for the Wager Races. I don't want to say much about it yet as I'm still not 100% confident that what we're doing is okay on a technical level (given the hardcoded checks associated with Wager Races) but assuming it continues to work out, we think it'll be a lot more enticing and interesting to play than the Wager Races ever were.
You will be able to commandeer at least 11 new cars (including the DM4 Family Sedan and the new bonus cars) in this version. Some cars from the base game may have their models tweaked slightly to add a bit of extra flair as well as having their stats adjusted to suit being in a different level than they originally were.
Homer and Bart's outfits are done while Lisa and Marge's outfits are only half done.
Several NPC characters also sport additional outfits such as Barney's Plow King outfit that was shown quite some time ago.
Tyler and I have discussed card ideas a whole lot. At this point the art and text for the Level 1 and Level 4 cards are done and implemented and we're discussing what the other sets should be. The actual locations of the cards has not been fully decided upon yet.
George and I have been discussing the appearance of the cameras and how they should behave but for the most part, these are not implemented yet.
Over the past couple weeks, I've been putting a lot of time into gutting old code from Donut Mod 3 and to a lesser extent Road Rage Returns and replacing it with newer and better systems. These include things like the rewards handler, sound resource management, script command registration, various utility functions and more.
As it stands, I'm now much happier with how the mod's internal systems work and I think we're now at a much better place in that regard.
We're really hard at work on the Mod and we're starting to see the light at the end of the tunnel now. We're really excited to finally have this mod out to you in the coming months and all we ask for is your patience. Thank you.