If it happened, rampant inflation, salaries rising at a slower pace than consumables.
Local government would likely ramp up local taxes. Property taxes would increase, etc. Government would freeze public sector salaries or rise them at nominal rate below inflation.
Capital controls could come in. Getting goods, services, capital, persons (bedrock of EU freemarket) in/out of country could be made more difficult.
Best protection IMO - gold and silver (hidden and in personal possession!), overseas diversified assets (stocks, commodities, property, bonds, currencies).
Regardless of the EU collapsing or not, I agree with Marc Faber who says that a 50% destruction in peoples wealth in the west over the next decade.
Capital preservation is the name of the game. Investing for income and trying to avoid the prying eyes of bankrupt governments attempting to take one's savings and investments through stealth or inflation.