There is absolutely no reason to seize coins which haven't been used in a "while". It is theft. Pure and simple and worse it isn't even necessary.
While I agree completely on your position and explanation (every quantity of money is sufficient and perfectly functional for a good economy), I do not agree that this can be considered "theft":
- refresh the deposity every 10 years (or every 1 million blocks, or whatever it is) is simlple to do by hand and completely automatable, so without any risk of "theft"
- reclaim of lost bitcoins must be made from miners, and so it needs a lot of work for it, and this gives them incentive to mine. So this enables to have less transaction fees.