He said he's aware of the horny bard stereotype and is specifically trying to avoid it.

The game map does include several spiral staircases that are "collapsed" or "damaged." I may add one of these, but I don't think it's likely to be an issue. I have remapped all the floors in MS Paint (it's ugly) and split off the chapel from a bedroom. I guess it's not a chapel yet, maybe a monument or trophy room?
The golems in it do not make sense as something the invaders brought along, so I'm going to say there's a golem there (clay or iron) but that Nalia doesn't have the activation token for it (her father does, and he's dead). Still, she can get past it and retrieve "weapons stored there that nobody was actively using" for the Elven Court Bow and Frostreaver and the flail head.

Even if Nalia does come along she will want to leave the golem behind to help defend her family's castle.

I'm going to say that Lord De'Arnise is down in the basement/dungeon at a treasury type area, but it's hidden or locked up, and the trolls failed to get the info from them. This will allow Nalia to have funds to reward the party appropriately, especially since they are going to skip/miss some of the GP-based rewards, like looting Lord De'Arnise's body.

At this point, the only PC who may wield the Flail of the Ages is the cleric. It'd be an upgrade from the Gnasher.