I bought the RC and have been very tempted to do this myself. Something about the 3e combat system makes my head hurt when GMing, all those squares - running it is like a chore rather than the pleasure of 1e; I keep thinking that if I ran OD&D the problems would disappear; though there are plenty of Od&D things I don't much like, like useless Thieves and weird saving throw tables.
Re the Dominion Management System - I've never used it exactly as written (calculating how stable the dominion is etc), it seemed a bit arbitrary. I do know that its "1XP per gp of tax revenue" is not a good idea for any but the smallest Dominions, far too much 'free' XP. The 10gp worth of 'service' per family/month also seemed too much. The list of possible events per year is a handy guide, rolling for 1d4. events/year works well. The Dominion Revenue by Resource Type table works very well and makes some areas more valuable than others, which is sensible. Population growth is too high except for 'gold rush' areas, for large kingdoms I generally use 2%/year if there's excess land. War Machine works brilliantly for resolving huge battles, the results are quick & plausible although you may wish to stat up Basic Force Ratings differently from the given system, which IMO underplays level/hit dice compared to training (average level of troops x2 = the add to BFR, whereas Training gives up to +52 BFR).