By brute force just as ethnic cleansing that occurred in OTL? Sure, Serbs in Krajina and Kosovo and people of all greeds and ethnic backgrounds living as internally displaced persons in BiH still don't accept what happened to their "purged" home territories, but it still happened and they have to live with that.
Yep - in January 1993. During 1992 it was still a fledgling alliance of militias and was just forming up. It's true that in OTL Armija was able to stand it's ground against their opponents, but assuming that both Croatia and Serbia gang up on them with their regular armies as well (nearly impossible, I know) they would most likely have to give ground until both sides state that they've achieved their war aims and dig in to the conquered territories. People fighting for their lives and homes are never a push-over and it wouldn't be the case here either, but I fail to see how Armija would have been able to stop such attack from happening. This scenario naturally assumes that Serb and Croatian nationalists somehow agree to focus on Bosnia and find some kind of a negotiated solution to their other disputes, so it's really, really unlikely to occur. Still, as a whole both sides had leaders who were mostly in control of the different armed forces on their disposal, and they made the political and military choises that led to OTL situation. To change that so that Serbian nationalists would reach a situation they'd see as "victory", one has to change the OTL situation quite a bit, and first and foremost remove the war against Croatia from the equation.
I'd also like to emphasize that we're discussing how and if Serbia could have won the war in Bosnia - not whether or not it would have been a good or a bad thing.