I think there is some merit to the suggestion. When maintenance is revised, the costs will be tied to aircraft utilisation, so in effect, not using an aircraft will lower long term maintenance costs. I think that, under such a system, it makes sense to partially tie aircraft value to utilisation too (as a well used, worn out, aircraft is going to be worth less than an unused one). In effect, I think a new maintenance and value formula could implement a large part of this suggestion.
The idea for long term storage has been brought up before, and I think it has been fairly well received. I don't think it is too much of a priority, but I don't think it would hurt to have an additional feature to mothball planes. I think that there should be some, albeit considerably reduced, maintenance costs for the aircraft. I would agree with the idea of having a 24 hour period to bring the plane back into service - which would discourage people mothballing planes to avoid a day or two's maintenance costs before they use the planes.