If you want old school, then play old school. What would be the point of using a
4E rules system then changing the majority of it?
Choose the system that fits the playstyle and needs of the group.
If game balance enforced at the per-round level is needed to make a group happy use
4E. If the group likes ultimate freedom with a high degree of uncertainty then use OD&D. Pick any other edition to get something in the middle.
Mechanics matter a lot in relation to the feel of a game. Whenever the need is felt to ignore the majority of mechanics then its time to shop for a new game.
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