I'm playing as Austria, Emperor of the HRE, and one of the electors was recently fully annex by a neighbouring state. I can now choose to replace them, and grant another state in the HRE the status of elector (allowing them to choose the next emperor).
What factors should I consider in my decision to choose a new elector. Obviously a nation that has good relations with me now is more likely to vote for me in the short term, but are there any long-term effects I should watch out for (nations with the potential for expansion, weak nations, strong nations, nations that border me, etc.)? Or, are there good reasons for not choosing a new elector at all?