On paper, French presidential favorite Francois Fillon's free market plans to cut business taxes, relax labor laws and shrink the public sector should give corporate France a shot in the arm and boost economic growth.

But his reforms are likely to come at the cost of showdowns with labor unions and public-sector workers who face losing jobs in a country where strikes can often drag on for several weeks if not months.

He could also clash with Berlin over a ballooning budget deficit, while a sales tax hike that would help pay for his other plans risks dampening consumer spending.