I inherited Flanders (which I'd made Burgundy release as a sovereign nation ages ago) and I now have three provinces in what was once Flanders that have this decision available. I took the decision in Nassau to see what happens - Flanders is reborn as a OPM in the form of Nassau.
What gives? What's the benefit of doing this? I saved before taking the decision and have since reloaded, but would like to know whether there's anything useful to this decision on my end. It has something to do with the HRE, but what exactly? The mouse over tip is spectacularly unhelpful ("(Austria): Event 'The release of Nassau happens'.")
In a similar vein, is it worth getting the province to leave the HRE? I'm England btw, so not a member of the HRE. From reading the wiki I gather that Austria (or whoever is Emperor - but right now it's Austria) has a CB to take imperial provinces from non-members.