Well, bright side: you're in business class, so even when they put you on Skyteam you still get most of the benefits you're used to.

13 trips in paid C might still put you at one top-tier and a mid-tier, depending on the eventual distribution across the three alliances.

Honestly, the thing that would bother me most about this policy is the extra segments they force upon you just to save a few bucks. NYC to most major German airports *should* be nonstop on UA/LH. Saving 3-4% on airfare and adding a few hours and additional delay risk to your trip by sending you through AMS seems rather foolish from a business perspective.