Can a Level 6 Kensei Monk make an improvised weapon magical?

Question

I've been scratching my head for a while in order to somehow manage to make an improvised weapon magical (to overcome resistance/immunity to nonmagical attacks). I believe I've found a way, but I want to verify it here first.

First, here are the relevant Way of the Kensei monk features (Xanathar's Guide to Everything, p. 34-35):

[3rd level:] Kensei Weapons. Choose two types of weapons to be your kensei weapons: one melee weapon and one ranged weapon. Each of these weapons can be any simple or martial weapon that lacks the heavy and special properties. The longbow is also a valid choice.

[...]

[6th level:] Magic Kensei Weapons. Your attacks with your kensei weapons count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Now, here are the relevant Improvised Weapons rules:

Sometimes characters don't have their weapons and have to attack with whatever is at hand. An improvised weapon includes any object you can wield in one or two hands, such as broken glass, a table leg, a frying pan, a wagon wheel, or a dead goblin.

Often, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM's option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.

Now, let's say you have a level 6 Kensei monk that chose "club" as one of its Kensei weapons, and wields a table leg. When the monk hits an enemy with magic resistance (or immunity) to nonmagical attacks, can his damage be considered magical (if the DM agrees that the table leg works as a club)?

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Note: I am fully aware that is it not optimal, but the build I have in mind involves 6 levels of Kensei monk and at least 6 levels of Tundra Storm herald barbarian in order to freeze water into ice, then use the ice as improvised weaponry (but treat the improvised weapon as a proper weapon chosen as kensei weapon in order to overcome nonmagical damage resistance/immunity). Now, determining which weapon is closest to a block of ice (in order to select it as the kensei weapon) is another set of gloves.

Answer 1

In your scenario, yes, a table leg can be treated as a Kensai weapon and thus overcome magical resistance.

Improvised Weapon [...] In many cases, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club.

In another situation, possibly not:

Kensei Weapons: Choose two types of weapons to be your kensei weapons: one melee weapon and one ranged weapon. Each of these weapons can be any simple or martial weapon that lacks the heavy and special properties.

An improvised weapon must be similar enough to a weapon on the simple or martial table (DM ruling) or else it would not work as you say.

As to your note added in the edit: Yes. A block of ice frozen in the shape of a club would count as both an improvised weapon and a simple club. If it breaks, it might become an improvised dagger (also a Kensai weapon).

Answer 2

Yes: Kensei can make the weapon's attacks overcome resistance

A monk is already proficient with a club. The class feature that the monk is using doesn't create a magical weapon; it uses ki for monk weapons and unarmed strikes.

For all monks ...

At 1st level, your practice of martial arts gives you mastery of combat styles that use unarmed strikes and monk weapons, which are short swords and any simple melee weapons that don’t have the two handed or heavy property.

Kensei gets around the limitation (italicized) with a class feature; pick a weapon and it's a monk weapon.

At sixth level, the monk's attacks do more damage than an improvised weapon does

The PHB table for Martial Arts shows that monk weapons and unarmed strikes, per the above feature, does 1d6. A club does 1d4. (Basic Rules, p. 46, Weapons table).

Using the improvised weapon will reduce the damage done to the target unless

1. The DM rules that it is close enough to "club" to fit into the above mentioned proficiency; monks are proficient with clubs be they Kensei or no.
2. The Kensei monk feature is used for that weapon

Given the title of your question, I'll repeat this bit: the class feature does not create a magical weapon; it provides a means to attack such that resistances to non-magical weapons is overcome. The active agent is ki.

Recommendation: hit them with an unarmed strike

Using an unarmed strike is a less complicated way to do magical damage than the proposed application of an improvised weapon. Granted, overcomplicating things can be part of the fun of D&D; been there, done that, and enjoyed it.

Or, choose that unconventional weapon as a "Kensei weapon" and get the monk weapon benefit, and a magical attack.