Sounds like an inflexiable Catalan or a tempo down Tarrasch. Are you thinking about a particular position?
b3 in the QGD?
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Thinking along the lines of a Catalan. I like to play my bishop to g2, but I get stressed out worrying about how to recapture on c4 if he takes. Seems like b3 does the job, as well as nicely allowing my dark bishop to go to b2.
Early b3 in the QGD can be extremely dangerous if you allow Nc3 Bb4 ideas so be careful about that. Also playing this way you may transpose into a Tarrasch or hanging pawn positions so you might want to get comfy with that.
What do you think about playing an early b3 as White in the Queen's Gambit Declined? The idea is to protect the c4 pawn to allow the light squared Bishop to go to g2.