Thanks.

I have played as Roma between 399 and 411.
First some minor notes:
* The nations you can choose from in the bookmark should be changed, maybe Roma, Constantinoblis, Franks and one or two other nations.
* Many ships are not visible. Only if they carry military units they are visible with only the unit avatar and flag visible. I noticed the Visigoths, Jutes and the Picts have this error. Maybe other countries. My own were visible. I dont know if missing graphical_culture might be the reason. However, land units are visible.
The game:
In this game a lot of nations declared war against me right from the start like normal. And like in the other games it was very difficult to deal with all those enemies. To quickly end some of the wars I had to accept to give away a lot of provinces to Franks and Visigoths. The Burghundians and Alamanns I could hold off with the military I could afford with the remaining provinces. Most other wars I could end accpeting peace by paying some or little money.
But now I had a lot of revolts going on and a Africa usurper was created, but I could end the war relatively quickly with a peace offering. In 407 I had peace for the first time...

With the remaining provinces I could not have enough military to deal with the revolts so about 409 my country broke down and Gallia, Rhenia, Hispania, Britannia, Pannonia was created from the rebels and I got stability 3 again... When the country broke down I also got a lot of military but that exeeded the force limit, so I had to delete most of them.
Conclusion:
IMHO the correct balance is not in place at the moment. You can try to train a lot military to defend youself in the wars, but the force limit is too low to do that. You can train enough to just reach the force limit, but you will not have enough military power to defend. You could concentrate on defending certain provinces, and then accept peace with the nations you have no chance winning against. But the longer the wars the more rebels you will have. And which way you ever take the result will be the same. You will loose your provinces and end up with a smaller Roma and a lot rebels, and Roma will eventuelly break down. If you can hold your enemies and the rebels off the usurpers will take your provinces. When the peace is over, you enemies will declare war again... wars never end.
I think the country modifer westromedecline is too drastic. -75% land force limit, -75% tax income, -75% manpower, -50% naval force limit... its just too much together with the wars that are started and the usurpers and the results of that meaning high WE and rebels. No matter what happens, after maximum 10 years Roma will be reduced to no more than one or two handfull of provinces.
Could I have done anything that could have produced a better outcome?
In all my games ERE holds almost the same provinces as when the games started even if its modifers are -25%. We could reduce the modifers for WRE to -50% or -40%?