As per KG & buffalo's comments, almost all of this if not all if this exists already. I think that because you're only Level 6 that you likely haven't unlocked a lot of the functionality to be able to create your own games like this, but the functionality is there. Also there are mods where members can write their own code to augment the game, so even if there is something new, it can be added by someone with coding skills (and membership). But most exists already, you just need to figure out how to use what's here to create what you're looking for.
For example:
1)
1- Different Multi-Attack modes.
- a. Double Mode >> w/ forward any amount or all, b. Triple Mode >>> w/ forward any amount or all,
c. unlimited chain w/ forward any amount or all. Currently the forward march is restricted to 100.
Please adjust for large numbers up to xxx,xxx (or 100,000) armies.
You can move any # of armies from 0 to your max available. What you see as the max of 100 is simply a default #. Just type in a different # and it'll move that many. As you level up, you'll also be able to move a % of your units, so you can for example move 70% one way, 20% another way and leave 10% where they are, etc.
2)
6 - Natural Disasters. Add another layer of realism. For example, every fourth turn you would lose X% of your forces to Malaria. Landslides. Desertion due to low morale. Earthquakes. Typhoon. Hurricanes. Tornado.
There is Pestilence, and likely the types of effects you're looking to apply with Earthquakes, Typhoons & Hurricanes (aren't these the same thing? Same with cyclones, just a matter of where in the world it occurs governs the naming convention), Tornados, can be achieved with Bombs or Nukes which exist already.
3)
8 - Limit cards. Sometimes I think it would be better if the total amount of cards was capped.
100% exists already - assume you just missed this.
4)
9 - Real historical battles and set ups.
People do this all the time. What is missing in your opinion to achieve this? See "Custom Scenario". But again - you won't have this unlocked @ L6.
5)
10 - Missions. As it is now, you're not finished until the map is beat. What if we had scenarios, like Search and Destroy? Espionage. Stealth and covert ops. Rescues. Insertion and infiltration. Missions was a lot of fun and would like to see it adopted here. Team Mission was also fun.
Many people do this via a variety of methods. See this game for an example of how I've done some missions myself:
https://www.warzone.com/MultiPlayer?GameID=22650475. There is also a mod "Winning Conditions" that has additional functionality, but you need to be a member to use it.