Hello. I feel like having bold field lines is not nearly as important as having a flat playfield, and anything on top of the already flat playfield will leave a ridge, bump, hill, however slight will affect the ball rolling over it. If you're handy and ambitious you can replace the playfield, a new one from Tornado is something like $250. If there is no damage or warping to yours I would leave it how it is. You don't need bold lines, look at Bonzini tables, they have no lines at all.