If you're serious about your chess (which it sounds like you are), I'd head for 1.d4 right away instead of messing around with 1.Nf3 and 2.b3.  Not that there's anything wrong with those moves, but if you're serious about improving you should jump right in and start studying the main line closed openings after 1.d4 and 2.c4, instead of concentrating on a "system" opening.

Note that when I say "main line" you have a lot of choice: against the QGA you could play 3.e4 or 3.Nf3, against the KID you could play the Classical, Fianchetto, Saemisch or others, against the Semi-Slav you could go for 5. Bg5 or 5. e3 ( and then either the Meran or various other setups), etc.  It's a lot to look at, but you'll get an excellent chess education.   

One last thing: if it's all about improvement, don't be afraid to start playing these lines in tournaments after only looking briefly at the theory.  Below 2200 (or maybe below 2000) few people really understand their openings well enough to punish you for making sub-optimal moves.  I, and GM Yermolinsky seems to agree with me in his The Road to Chess Improvement, believe that the best way to start learning an opening is to go ahead and start playing it.  That way you'll really be forced to think about your position instead of just mindlessly following theory.  After the game, of course, go back and look everything up.  This way you'll learn openings faster because you'll start to understand the moves instead of just parroting a bunch of IM/GM games.

1.b3 or 1.Nf3 and 2.b3 could work as a compliment to the dutch, as black ideally wants to fianchetto the Q's bishop but rarely have the time. 

On your level you could expect many games to start like this approximately:  1.Nf3 d5 2.b3 c5 3.Bb2 Nc6 4.e3 e6 5.Bb5 Nf6 6.Bb5 Be7 7.Ne5 intending f4, 0-0 and a k-side attack...

You get your own kind of game, and there's not much theory. (I only recall one book about it, by Joanathan Tait in the late 90s iirc). Admittedly, there's not much advantage if black knows what to do but it's solid and not completely without ambition - after all, on a good day it's a QI / NI with an extra move! 

I'm looking for a "once-and-for-all-time" white repertoire to complement my French/Dutch as Black.  After tactics and endgame practice, I have about an hour a day to look at openings.  I want something that will last till I die, that's effective, and that I can have fun and grow with.  Thanks for any help or advice you might have to offer.  I'm rated about 1650.