I think a better approach for coins redistribution would be to create thresholds for three classes of accounts:
1) spam/dust account x < 0.5 mc
2) low income account  0.5 < x < 10000 mc
3) high income account x > 10000 mc

Then the rules would be the following:
 - spam/dust accounts gravitate to zero over time (decay with fees)
 - low income accounts gravitate towards middle threshold 10000 mc (grow with interest)
 - high income accounts gravitate towards middle threshold 10000 mc (decay with fees)

EDIT: plus add the rule that if any account hasn't been spent from for a period of time,
the interest (if any) drops to zero, the fees start to apply (if haven't before).
This will allow dead accounts no matter of which class to eventually decay to zero.

Just my two cents.