Hosted bar

@OP, what you described above, to me sounds like a good plan. But you could scrap the mimosa bar and signature drink and do beer and wine all night for probably the same price as liquor tends to be more expensive. This way you wouldn't have to worry about running out or setting a cap and you'd still stay within the same price range Also, setting a cap is no fun - just because when the bartender announces, "15 minutes until cash bar" you just have people hauling ass to the bar, waiting in line, and leaving some people without because they didn't get there fast enough and that's no fun.

Beer, wine and champagne are fine for a wedding on any day, but do it for the whole night.

Sweetie, nothin' says lovin' like "go easy on me" and "I know this is a hot topic."

Host what you can the entire time, even if that means beer and wine only.

If you want to cut costs, cut the champagne. Most people wont drink it so you're going to be paying for something that wont get consumed, you can simply have people toast with whatever drink they have. I am also all for the wine and beer all night, this is what we are going to do along with cider since most of our guests are big into ciders.

Skip the liquor and you can honestly skip the champagne toast too like @Samantha said. Just stick to beer and wine all night.