The NATO Ultimatum Game

So, the US via SecState wannabe Rex Tillerson has offered NATO members an ultimatum--come up with spending plans to get to 2% of GDP spent on their own defense (no, Donnie, not dues owed to the US) or else.  Or else what?  No idea.

How should the other members of the alliance react?

1. Come up with an elaborate schedule and then not meet it.  Paul Musgrave suggested this after his talk at NPSIA today--that one of the things European countries do best is come up with various goals and then not reach them.  The upside is that Trump has a short attention span and no expertise (and does not listen to experts) so he may not detect that the Europeans are not doing what they promised. The downside is that Trump may listen to someone on Fox who does do a bit of homework and then he will rant some.
2. Spend more in the next year, as you were planning, and let Trump take credit for decisions made prior to his Presidency. 
3. Start counting stuff as defense spending that you previously did not, which each year counting a bit more.  Such as border security, veteran's benefits, whatever.  Game the numbers until Trump is gone.  
4. Tell Trump/Tillerson to fuck off and see what happens.  Trump can't pull out of the NATO treaty without Congress, but he can pull US forces out of Europe....

I'd like to see #3 because I hate it when friends threaten friends.  But I'd bet on one.  The reality is that most allies can't dramatically increase their defense budgets for a few key reasons. Canada demonstrates what happens when one does not have enough bureaucrats who are good at procurement--projects get delayed.  So, Canada can't spend the money it had allocated to this stuff.  A more fundamental reason is that countries have domestic politics and competing priorities.  The German foreign minister, who is of a different party than Merkel, has already said hells no to getting to 2% quickly.  This makes #1 unlikely for many countries since lying to the US would still suggest a commitment that some parties are unwilling to make.

Are there other options?