Looking at it from a Playable/ payable point,
Austria + Spain combination of large European power with another large Europen/ Colonial power playable but expensive to play for a single player
France + Spain Combi of two large European & Colonial Positions ( But France being played as a team position) Expensive but could be split between the three players, a possability still a major shift in game power.France is already seen as the Major power in game, combined in a team position with Spain will it ultimatley effect game balance?
Portugal + Spain smaller European Colonial position with major European colonial position, similar problems to the Austrian position is it too big for one player? Admitted Deacon has pulled it off, but has admitted it is very time consuming & can lean into the expensive direction.
Papacy + Spain small European position with potentially a lot of relegious soft power + Spanish Empire, probably the most playable/ payable position from a game point of view for a single player, some concerns about relegious side of matters & how powerful it would make Papacy in comparison to other Catholic positions & non- Catholic positions.
Which players are willing to invest more time & maybe more importantly more money into taking the position forward I realise this is moving away on a tangent from the initial proposal but maybe it is also a factor to be considered, in some of the above combi's there lies the danger of players leaving the game due to real world time& finacial matters, so instead of having just an inactive Spain there would be by default other vacant positions as part of the fallout. Hope players have taken that into account when they make thair bids for the position.
At the end of it all sits Agema who will ultimately make the choice one way or another, influenced by various in game player actions