You wont have to deal with coring costs then. I am currently playing as Austria, the year is around 1575 (maybe a bit more) and I have managed to pass 3 reforms. The prince crests in the HRE page show why they are for/against the reforms so you can see it in detail there.
For example Hungary sizes is too big to join but if it release Croatia as vassal first the he need +196 relation with the emperor to add provinces to the empire.After the Capital added the nation will become part of the empire. Bologna joined the HRE somehow but their opinion of me was only around 100. 1.You must win the election of the electors and become the emperor of HRE. But i can't find the lastest mechanics for joining the HRE. At this point, I don't know how get nations to join the HRE. Having done some research I think I can gain Imperial Authoirity by adding new nations into the HRE, and … There is any method for me to join … Nations can join to the empire if their size is not too big and have good relation with the emperor. Essentially, the key observation is that if you release non HRE vassals, they will auto join the HRE, giving you 10 IA.
