Each night, you can pick two simple weapons to master. A dagger is a simple weapon. It also uses your martial arts die for damage, just as it would today for Dedicated Weapon or Kensai.

Here is Nick:

When you make the extra attack of the Light property, you can make it as part of the Attack action, instead of as a Bonus Action. You can still make this extra attack only once per turn.

At level 1, there is a bonus unarmed attack on Monk - since that is not the Light property on a Weapon, that bonus unarmed attack can still be used. Flurry of Blows is also not the Light property on a weapon, and so it'd also be open - assuming you took Two-Weapon Fighting, you would make that attack with your ability modifier and your martial arts die.

And so that would increase all the numbers by the martial arts die, and then by the attribute modifier as well if you had two-weapon fighting. This would put it very much comparable to the Warlock Baseline that was recently posted here.

A friend once told me, it was for Xcom and EverQuest back in the day, that there's a secret in all games. I will share his wisdom. "When you don't hit, things don't die." So, if you're looking at anything that improves a hit rate - it will tend to improve your damage over time more than something that merely improves damage, unless the damage boost is ridiculously overpowered.

To me, this is the principal behind a lot of high damage builds - of any class - the principal of "my attack bonus is high, and I roll the die many times." And that's because consider Disintegrate, for example. It is a great spell - it does a lot of damage. But it is all or nothing - either the spell gets you or it doesn't. Again - it's a great spell, but either it works or it doesn't - and if it doesn't you deal none of that damage and may not have the spell slots to try again.

If you look at the Monk - there's another thing to consider here, which is stunning strike.

When a creature is stunned, you get advantage on attacks and prevent it from doing anything, so you can attack.

That is pretty good actually! Though I can see some Monks disliking that they have to optimally use a weapon and not stay unarmed. Cool for a ninja-themed Shadow Monk though.