Be aware that Wikstrom's and the Swedish Bakery can be truly PACKED at holiday time. If you call the Swedish Bakery and pre-pay you can take the express lane: a plastic number (vs. the plebian paper). I have ordered special-occasion princess cakes with various fillings. IIRC apricot filling is available on special order, if you want to try to achieve the Battenberg combination you mentioned. However, you may have to ask for the special occasion coordinator, as they don't usually make apricot. The mango is great if you want another option.
By the way, while you are waiting, you might have time to wolf down a semlor. (My sense of aniticipation for the marzipan is almost always insurmountable.) And besides, semlor are comparatively sensible treats: a yeast bun, (not sweet, but lightly dusted with powdered sugar), filled with a slice of marzipan and unsweetened whipped cream. Not a wheatgrass smoothie, but your teeth won't ache, and you'll preserve your appetite for the actual cake event.
Man : I can't understand how a poet like you can eat that stuff.
T. S. Eliot: Ah, but you're not a poet.