There was nothing wrong with Blood Money's method of disguise. You killed dude, took his outfit, you were that dude. Job done. Unless you did something messed up or out of place (killing someone for instance) you were fine.
I'll give you an example of how janky and fucked up the disguise mechanic is in this game. I could load the Terminus level checkpoint, where 47 leaves the elevator. He's wearing the outfit that the baddies are all wearing. AS SOON as you leave the elevator, you are in direct view of enemies, so I'll take an immediate left around the corner. AS SOON as I walk toward a guard, he'll immediately start to suspect. It literally takes a few seconds for him to take offense and try to stop you to see just who you are. You can use your instinct, but since one of the most crucial aspects of the Hitman games is exploration and seeing just what you can do with what you have, so that instinct becomes quite useless once it's gone and you're surveillance is somewhat complete.
Somehow each person you are disguised similarly too KNOWS who you are within 5 seconds. You try to walk away? Guess what, you might as well just restart there because you're already a suspect, and you're already gonna get "arrested" and that will lead into a shoot out. This is even more apparent in the later difficulties. So this is my problem with the disguise system, it punishes you for blending in, which is what Hitman games have been about. A silent, efficient assassin.
Like I mentioned previously, Blood Money did it fine. I dislike this phrase but why fix what ain't broken?