I'm very flexible on this, and if we agree to hit Russia soon that's totally fine by me, however I'd be inclined to take Catherine's Defensive Pact immediately, and just roll over that variant requirement now.
The city of Yayoi has always bugged me, and I'd just like to take it off Gustav's hands from an 'annoyance factor' largely. It's a nice little commerce spot that would make a fine addition to our Prussian-French empire. If we take the Russian Defensive pact, then hit the Vikings, then we're free to take on Russia without being concerned on whether we need to; cap' her, or destroy her, or if things go badly settle for peace before capitulation is secured. Anyway - thought that I'd toss that one into the mix.
I agree with nocho that getting Bursa and Konya would be a good objective. Also agree with vranasm that 21 Cuirassiers is 'OK' but could sure be 'added to'.
As such, my leaning (without being fanatical about it) is to sign a Defensive Pact with Russia, think seriously about capturing Yayoi, and preparing a bigger invasion force against Ottoman-HRE or Russia ... such as a dozen more Cuirassiers.
I'm a traditionalist, so I'd build an Academy in Hamburg to support our Oxford Uni' city. Super-Medic the Great General with a two-move unit, such as the 5XP Cuirassier in Marseilles.