When playing a catholic nation trying to stop the reformation, your success depends a lot on where the centers of reformation spawn. If a CoR spawns in an OPM, or the capital of a smaller country that you can force convert at once, you can quite easily stop the CoR. If it spawns in the capital of a larger country, you can force convert after some more wars, which is fine, it should be more difficult to stop religions supported by large countries. If it spawns in a non capital province of a large country, you can perhaps force to release a country whose capital the province becomes, and force convert that country, again, fine.
If the CoR spawns in one of your own provinces, or a province of one of your subjects, you either have to wait for 30 years or release a vassal or your subject and then declare war on them. Assuming there even is a suitable core on the province so that you can release a vassal. Thus it is harder to stop a CoR that spawns in your own province or a province of your subject, than a CoR that spawns somewhere else.
To fix the above, I suggest that placing a missionary to convert a province with a CoR stops the CoR from propagating religion as long as the missionary is there, even when the missionary is not making any progress. You can think of it as the missionary being in a theological debate with the reformers. That way the CoR and the 30 year ban on reconversion still matter, by taking up a missionary and his maintenance cost, but stopping CoR that spawns in your own country is no longer too hard compared to stopping one in another country.
While on the subject of missionaries, perhaps one should be able to override the missionary of a subject. For cases when the subject takes 100 months to convert a province that you could convert in 10.
If the CoR spawns in one of your own provinces, or a province of one of your subjects, you either have to wait for 30 years or release a vassal or your subject and then declare war on them. Assuming there even is a suitable core on the province so that you can release a vassal. Thus it is harder to stop a CoR that spawns in your own province or a province of your subject, than a CoR that spawns somewhere else.
To fix the above, I suggest that placing a missionary to convert a province with a CoR stops the CoR from propagating religion as long as the missionary is there, even when the missionary is not making any progress. You can think of it as the missionary being in a theological debate with the reformers. That way the CoR and the 30 year ban on reconversion still matter, by taking up a missionary and his maintenance cost, but stopping CoR that spawns in your own country is no longer too hard compared to stopping one in another country.
While on the subject of missionaries, perhaps one should be able to override the missionary of a subject. For cases when the subject takes 100 months to convert a province that you could convert in 10.