Because 4e is rules transparent, and because the offense and defensive value of magic items are balanced with each other, you could toss magic items completely out of the campaign, modify monster levels slightly, and play with minimal disruption.
You can tick the 'inherent bonuses' box in the Character Builder and use monsters exactly as written; I'm not sure you even need to reduce energy attacks. Maybe reduce monster status-condition attacks a bit in Paragon & Epic to compensate for PCs not having item powers.