It seem feasible to do both as you guys have said but then aren't we tagging two people when only one character appears in the issue? I say we let Dan Slott decide! Man am I gonna give him a hard time at London Comic Con! :)
There's a number of character pages on Comicvine that say something like "Tony Guerrero is the current Hero Bloke, previous Hero Blokes have been xyz" so maybe on Spider-Man's page under Current Events we can write Otto Octavius' mind is currently in Spider-Man's body or some such. Then keep tagging Spidey and let him rack up those appearances.