There isn't a whole lot of room to manoeuvre.
Sanremo, De Ronde, Roubaix, Amstel Gold, Liege, Giro, Tour, Vuelta, Worlds, Lombardia have to be in there. Fleche Wallonne and Gent-Wevelgem fill in gaps.
That means Pais Vasco, for example, isn't really viable.
The remaining races are filling in the gaps in the calendar.
So it could be:
Paris-Nice vs Tirreno-Adriatico vs Catalunya
Dauphine vs Suisse
Pologne vs Eneco
Quebec vs Montreal