Marandahir
Crown-Forester (he/him)
Not according to RAI. An Improvised weapon is not a Melee nor a Ranged weapon. It can be used to make melee or ranged weapon attacks, but as with unarmed strikes it doesn't gain proficiency bonus and isn't a weapon itself.They can benefit from nearly all of the fighting styles.
A chair leg in one hand is a one-handed weapon. A ladder is a “weapon used in two hands”.
TWF relies on a DM may I, so don’t take it without a good talk with your DM.
Mprorection requires a shield, archery is self explanatory.
Haven’t looked at the Tasha’s options.
You might play DM-May-I to ask the DM to treat the chair leg AS a club to gain proficiency, and I'd suggest in those cases you'd be able to take advantage of archery, TWF, GWF, Duelling, etc.
But even a ranged weapon being improvised to make melee attacks (i.e., hitting you on the head with my crossbow) is not a melee weapon, it's an improvised weapon used to make melee attacks, and vice versa for a melee weapon thrown as if it were a ranged weapon.
Protection is no good for the Brawler because a Shield takes away your unarmed expert feature.
Interception requires a shield or a simple or martial weapon, so no go with improvised weapons and unarmed strikes.
Unarmed fighting is redundant as all its benefits are subclass features here.
Surprisingly, I think Thrown Weapon Fighting works with the Brawler, as it doesn't specify melee or ranged weapon nor martial nor simple weapon, just a thrown weapon (which improvised weapons can be). So I guess that's a grand total of 4 choices for the Brawler: Defense, Thrown Weapon Fighting, Superior Technique, and Blind Fighting. And all save Defense require buying an additional book.
That's what I mean. As you said in your post, this subclass seems to be mechanically at odds with the themes it's trying to represent.