I wouldn't mind if the 5 Euro bills were replaced with a coin, provided some of the lower values (Euro 0.01 and 0.02, perhaps even 0.05) would go.
Switzerland is almost like that, they have 5 CHF coins (3.5 EUR). I wouldn't mind it if they did something similar in Norway (turning 50 NOK bills into 50 NOK coins (6.3 EUR). But, we already have 20 NOK coins (2.5 EUR), so it's not that bad. As a side note, our least valuable coin is 50 øre, which is 6.3 Euro cents. We're talking about removing it in favor of just using 1 NOK as the smallest coin (12.6 Euro cents). I haven't seen anything costing less than 1 NOK since the early 90ties, so I don't think it'd have a huge impact (some sweets etc that are 2.5 NOK now, might go up to 3 NOK, but that's about it).