I know you're dealing with the after effects of the civil war you went through, but you could consider this offer after you're done with that.
You could potentially gain more if you side with the Entente. With you we could easily destroy the Central Powers in Europe.
What we offer:
1. To make up for the Russo-Japanese War, we can set up a peaceful agreement between you, Japan and China and a fair partition of Sakhalin and other contested land.
2. If you choose, we can get you land in Asia in the form of Persia, Afghanistan, and (maybe) Mongolia.
3. Free reign to do whatever you want with the Danubian land East of the 17th Meridian East.
4. Gains in the Baltic and North Seas in the form of a German puppet state (or annex it) consisting of the state of Mecklenburg-Vorpommern, the cities of Hamburg, Bremen, and Bremerhaven, and the state of Lower Saxony
5. A puppet state that gets you access to the city of Istanbul and the Bosporus straits into the Mediterranean, and as much land as you want in Eastern Turkey
6. Do whatever you want with all German land East of the 10th Meridian East.
7. Assistance improving your economy, building up infrastructure, and modernizing your military.
8. If you want, we can arrange getting you a colony in Africa, the Middle East, the Pacific, or the Americas.
9. A 10-year joint occupation period of Berlin and Vienna.
10. The restoration of your allies in the Balkans (Serbia, Greece, Montenegro) with pro-Russian Governments
11. A fifth of the war reparation money that Germany, the Ottomans, and Danubia will pay us
12. If you want, you can have Alaska back from America, and if you want you can also have the Hawaiian Islands.
13. We will help you make a functional Air Force and make powerful, faster planes.
14. We can also introduce you to tanks and heavy artillery.
15. Free, unrestricted access to oil reserves in the Middle East and Africa. We will also assist with your own oil-drilling program to get a boost in your economy.
16. Free, unrestricted access to Dutch, British, and Danish ports to extend your access to trade throughout the world
17. If you want, you can our new global defense and economic alliance.
18. Do what you want with the American Pacific, as well as some of the Philippines
Some more reasons why we would be the better choice:
1. If you remember, before your civil war you were a member of the Entente. We are your allies.
2. We have the manpower advantage over the Central Powers for the time being. If you join now, when all of the German and Danubian troops are on the Western front, you could just steamroll through the Germans and reach Berlin in a matter of weeks or days. Danubia would be easy to finish off from there.
3. The Central Powers are only offering land. We are giving you the chance to improve the well-being of your people and stabilize your country.
4. You're already a very strong country, but with our support you could rise to superpower status.
5. Join us, and Japan won't need to be your enemy any more.
6. With our help, you could unite all the Northern Slavs of Europe under one flag. If you join the Central Powers, there's no chance of that happening.
7. If you ever become unstable or need help keeping your country together, we'll have your back and be right there to help.
If there's anything else you want, tell me and I'll see what I can do.
If you want the whole deal except for one thing, just tell me.
It's understandable if you don't accept.
Remember, you can choose to only accept some of these terms. If you don't want the land, we can figure out a use for it.