Cannot equip rapier with a dagger offhand. Considering this was a style of combat all its own during the Renaissance, I can only assume this is an oversight.
Technically, this follows the TT rules, and is not an oversight. Indeed, the Rapier is not a Light Weapon, and thus not usable with a second weapon in the off-hand.
That said, Rapier+Dagger is something I am requesting too. It looks cool.
As for how to make this happen, it's probably not a good idea to make the Rapier be Light, from a strictly mechanisms point of view (in reality, I would think a rapier is fairly light). Otherwise it would be Light and Finesse Weapon, like Scimitar and Short Sword, but dealing 1d8 instead of 1d6.
Instead, they should just say that Rapier allows you to have a second weapon, only if that second weapon is a Dagger.
This change would barely modify the "fine balance" of combat, and certainly would do so orders of magnitude less than plenty of other rules changes Larian is making. So "oh no it will screw the balance" doesn't really work here.
