D:OS is a pretty light RPG compared to Neverwinter Nights (D&D3.0 Ruleset) - at least considering character creation! What you are looking for is actually D&D 4e with minor adjustments - maybe give players more action points, rewrite some spells etc. But still D&D 4e gives you much more freedom in character creation etc. than D:OS. If you want more complex P&P try Pathfinder or D&D 3.5, maybe D&D Next. All systems can be modified to play a D:OS P&P.