What if the skills as described in the od&d red box core rules were replaced by the skills/dc system of 4e? Don't touch anything else, just replace the thief's 15% chance to open locks with a thievery check, his 10% chance to hide in shadows with a stealth check, and perform analogous functions for the other classes. Quite apart from how people may or may not feel about this change, what mechanical complications might arise from inserting this bit of 4e into OD&D? For establishing the scores, you would defer to the od&d ability score modifiers. For establishing number of trained skills, you would defer to the 4e rules on race and class.
