I'm not sure about ramifications for smaller peripheral nations. There are just too many unknowns that depend on how the EU breakup proceeds.

The most straightforward breakup scenarios are Brexit style nationalist movements in the countries benefiting least from the union. That could have a cascade effect, where the value of being in the EU declines for the remaining nations, leading more of them to leave.

I could certainly imagine the breakaway nations having better relations with non-EU members, but they may also go down a more protectionist road.