The first one that Tom linked is the only comprehensive attempt that I've seen. The problem is that everyone is different and has different wants, needs, usage, expectations and budget.
One could easily argue that there are NO necessary mods though the upgraded balancing lever "doohickey" and the thermobob are certainly highly recommended for almost all.
For example, someone doing mostly long distance road riding might rate panniers and racks, tank bags, 16 tooth countershaft sprockets, bar risers and taller windshields as desireable mods whereas my offroad biased usage means I value NONE of those things and concern myself with protection (bars, handguards, skidplates, low profile drain plugs, etc.) and functional improvements (suspension upgrades, brake upgrades, etc.)