Let me know if
Mook is a landscape, like an Event or Project. You can add a Mook to the game like you would any other landscape; alternatively, if one of the Kingdom cards has the Henchman type, you would add a Mook (if there wasn't already one available). You say:
There's a recommended max of one per game, like Ways.
During your Buy phase, you can spend the price on the Mook and a Buy to gain a Mook token to your Mook mat. You can also gain those Mook tokens by using cards with the Henchman type.
During your Action phase, you may spend one Mook token and an Action for the effect listed on the Mook.
Is this correct? If so, my thoughts are below.
This is an interesting idea. I have toyed with something similar: I had the idea of Skills, which were landscapes that a player could gain using a specific Kingdom card; each Skill had a cost in Actions, and could be used as many times as one could afford during the Action phased. I quickly shelved the idea as it would only really work with a ton of villages, which you would not otherwise probably want.
The idea of spending 1 token and 1 Action is definitely an improvement on my initial concept. However, I think there are some things to consider:
First, you say that only one Mook is "recommended", but I think that would actually need to be a rule. If they are going to be of different power levels, and therefore at a different price, then it is a problem that I can buy a Waif at $2 but spend my Mook tokens on a Bouncer that usually costs $4. I guess you could have different color Mook tokens, but that seems like an additional complication.
The second issue with the Mooks having significantly different power levels is that it makes the Henchman cards hard to design, especially in terms of price/balance. Getting three Waif tokens is a significantly different proposition to gaining three Bouncer tokens, so while the former is an easy pass, the latter is a must-buy. If you're going to use both the the Mooks and the Henchmen, the Mooks either have to all be at a pretty similar power level, or they have to cost a different number of Mook tokens. (If you did the latter, their $ cost could always buy you that many tokens, while the Henchmen would give out a fixed number).
Third, when designing the Mooks, you need to keep in mind that when comparing their effect to the effect on a regular Action card, the Mook has a hidden +1 Card. The parallel I would draw is that when you evaluate the "on the next turn" effect in a Duration card compared to an event, there is a hidden +1 Card, +1 Action (so getting +1 Card from a Caravan is the equivalent of playing a Lab, as the result is 6 cards in hand and 1 Action). Another way to think about this is that all Action cards have a hidden -1 Card -1 Action, because generally to play them you have to spend an Action and play one of the cards from your hand; this is why cantrips have essentially no effect, returning your handsize and number of Actions to where it was before you played it.
While still requiring you to spend an Action, Mooks do not require you to play a card from your hand. Thus, if you wanted the Mook Lackeys to simulate the existing official card of the same name (which is another issue, but I get that right now you're just floating a general idea), it should be +1 Card. (The net result of playing the card Lackeys from a hand of 5 cards is that you have 1 fewer Action and 6 cards.) Similarly, Bouncer is a Horse you can will into your hand at any time, which also protects you from Attacks until the following turn. I think this would have some tracking issues, and I'm guessing you didn't intend it to give both a protection and the equivalent of a lab.
Overall I do think the core concept is a good idea worth pursuing. I do like the modular format and the ability for that effect to be different based on a different landscape.
Regarding theme/flavor, I do think it's a bit anachronistic. It made me think of the scene in Robin Hood Men in Tights when Prince John and the Sheriff hire a mafia don (played by Dom Deloise doing a Marlon Brando impression) to kill Robin. There the anachronism is a joke, but here I'm not sure it works.
I do have a different suggestion. When I was designing my (absurdly oversized) Winter Gear pile for the WDC involving Snow, I looked into medieval snow removal, and found an "Ask a Historian" reddit page about it, where the historian quoted a passage from what was basically an operations manual from a medieval monastery about what to do when it snows, and one of the things it mentioned was hiring so-many "day talers" to do various tasks. The historian explained that a day taler (or daytaler) was a class of worker back then who would be hired on a day-to-day basis do various tasks (roughly the equivalent of what we would now call a day laborer). Ever since I've been thinking of ways a day taler might be used in the game, and this might be it.
Instead of Mooks, the landscapes could be Jobs, and mat could gain you Taler Tokens. Different power level jobs could require a different number to tokens, and the cost could indicate both how much it cost and how many Talers it gained. The Kingdom (or non-supply) cards could have the Daytaler type, and add tokens to the Taler mat.
It might look something like this: