Thursday is good. The tactic is to hold off from doing both Spire and tournament until the start of the FA. You can then use time boosts to finish the Spire. By this way, you can have two Spires and two tournaments during the FA.
I can see your point,
@Julian, and I know there are others like you, too, but I don't think the majority of players - many of whom are very far from your degree of commitment, experience, and size of Inventory! - will find this a convenient, or even possible, solution, so I'm with
@AuroraBolt on this.
While Time-Boosting the Tournament and/or Spire to the extent you've described is theoretically possible, of course, for players who (a) have enough Time Boosters (and many don't), and (b) want to spend them on something as transient as the FA (and again, many don't, since they're useful for so much else), but for those players who don't fall into both of those categories - well, for this one in particular! - it's really rather irritating that the FA is not timed to coincide with the greatest availability of the Tournament and Spire.
If the reason for the FA's current timing, as I've seen suggested, is because the developers need to be available for the start and end of the FA in case of technical errors, why not simply set the FA to begin on Monday morning (German time) and end on Friday evening? That would seem to suit almost everyone... except, perhaps, those players who would prefer to do the majority of their FA Badge-collecting on weekends (work/study commitments, or just personal preference), although [I know, anecdotal, but still...] I've found that such players are in a far smaller minority than those (working or not) who would prefer the FA to cover a Monday-Friday schedule, thus making the collection of the Tournament/Spire-related Badges (and the completion of both of those weekly events, as well) a far more natural and less forced/rushed affair.
In my opinion, the FA is already stressful enough for most non-FA-focused Fellowships, and I'd say that the additional problem of the FA's poor Tourney/Spire-related timing is just another reason why many FSs find some of their members less than keen to participate. The added expense of (a lot of) Time Boosters, only in order to 'force' the Tournament/Spire to fit around the FA (as shouldn't be necessary if the FA were properly timed) is not a realistic proposition for many/most Fellowships who are already having trouble motivating their members to compete in the FA in the first place.