Wasn't the earl of Derby also considered at one point?
That said, Affie's marriage to a Russian grand duchess was always on the cards. He was offered a choice, Tina of Oldenburg, Maria Alexandrovna, Olga Konstantinovna, and Eugenia Maximilianovna of Leuchtenberg. The only non-Russian bride ever mentioned for him - IIRC - was Elisabeth of Wied (later queen of Romania).
No French, British or Russian princes will be considered (I've scrapped Austrians since someone pointed out that short of a civil war, there's no way that the hyper-Catholic, hyper-Conservative Habsburgs will go to Athens).
Ernst of Coburg was considered, but there was some issue because he had no children (I've read - but been unable to look deeper into it - that he had three bastards, perhaps the GPs would be willing to accept one of them as heir, provided he marry a princess); as had been his uncle, Leopold of Belgium (as a British candidate in 1830). Leopold was first eager to go, but then he found out about the dismal state of the country('s finances) and decided to rather not. Either Coburg refusal shouldn't be too difficult to change.
A Battenberg Greece might also be interesting - this being post-Othon's deposition. No one seemed to have any major objections to Sandro becoming prince of Bulgaria, so why not let the tsarina's brother (Alexander of Hesse) become king of Greece?
A Beauharnais Greece would be interesting, but I fear that the idea of a Beauharnais as king of Greece will be viewed similarly to an Oldenburg being prince of Bulgaria - since in both cases, the other GPs (Austria, France and Britain) would regard the king as being on a Russian leash.
An interesting, if quasi-ASB candidate, is Pedro I of Brasil/IV of Portugal. He's Catholic but unlike the Habsburgs, I think he'd convert without too much of a problem.