Well I hate to disillusion you (it being New Year's Eve and all) but you'll not gain rank by helping Hudson in Powerplay, only by doing Bulletin Board missions (I've been a Hudson PPer for a couple of months now, and I still camped out at 17 Draconis to earn the rank for my FAS).
I agree that it would perhaps make sense for a number of other things to increase your rank, I guess it's done this way to slow down the rate of progression - I want to buy a Clipper, so I've been sitting in Empire space for about a week now doing endless missions....I'm at Lord 19% currently , when I get that up to 100 I'll make Baron and be able to buy it.
As I also did some undermining (killing imperials at CD-49 3617 to be specific) to maintain my Hudson rank 4 for the week I had to break off for a few hours yesterday, killing the Imps didn't alter my Empire rank or percentage but it did drop my Empire reputation quite a bit. I think you'll find this is where you'll notice some effect on ratings - doing stuff for Hudson will likely involve killing Imps, and that will increase your combat rating and - I think - your Federation reputation....but it qwill most assuredly not affect your fed rank.(A shame really, I'd much rather slaughter my way to the Clipper <g> )
Dave