That was the original idea, but it very difficult to implement, would require a hard-fork, and is effectively the same thing. Your idea is basically to give a discount for voting. Two ways of looking at the same thing.
It is not the same think if the result's are not the same...
"you would make many users to make random votes just to get ride of the fees"
how can we stop this kind of effect ?
PS The idea is basically to give a discount for right voting.
I think if they were to vote randomly then it would be noise in the system. My assumptions are:
1) most users want to do good and not harm
2) users have incentive to even think about voting which is the biggest task
3) if users do vote "randomly" they will likely vote with the majority (ie: current leaders) and make them stronger
4) "not voting" and "voting with the majority" are effectively the same thing, except that it makes it harder for an exchange to take over the network due to low voter turn out... ie: voting with the current majority is voting for the "Evil you know" rather than letting some future evil gain hold due to lack of votes.
5) Once they vote, they will likely have have experience with voting and will give it at least a slight positive bias.
6) Once they have experience with voting, they will be more likely to do it in the future.