TL;DR I don’t think Poles necessarily have to be a cavalry civilization
For what I understood (correct me if i’m wrong) you don’t fully agree with the way their Kinght line works, as in: you only have a boost going for knights in the castle age, but only in the small gap where you can get the castle tech before imperial.
While it is true that, if you want to play Knights with Poles, that is your strongest point, I don’t think that’s necessarily how you want to/have to play the Poles.
Follow me on this thought for a minute. If you are massing Knights (in the Castle Age), you first have to ask yourself: Why am I doing this? Their knights don’t scale that well into imperial like you said. So why force yourself down a “bad” path for your civ? If you’re producing knights, it should be to use them in the castle age, not to hold them or mass them for Imperial Age. If you really want to play stable, it could be a good idea to add hussars into the mix, which we can agree scale better for the poles.
Nevertheless, it is true that you can’t solely produce hussars in castle age, as they will likely fall against other gold units. So, in order to find a solution to this situation, why not play with archery range units? Poles have a nice range, only lacking last armor. Following this gameplan allows you to have a very solid archers + lightcav comp, which turns out to scale very well into the late game.
At this point, arb + winged hussars will do very well against any other cavalry civ. Poles’ incentive to mine stone will also allow you to get castles faster and gain map control that way, a very nice thing to have when playing archers.
The harder matchup will be against other archer civs, where the lack of Imp armour for hussars will definitely hurt, but then again, poles are very flexible and can add great skirms, rams or even bbc into the mix.
As for the castle age tech, I think its best moment to shine is if you intend to go all in in the castle age (delaying your imperial age until ~130 vils), and go for that tech with a lot of farms to spam. It can also be nice in imperial, as a flexible resource, but as I already mentioned I don’t think that’s their main go-to.
I think Poles are definitely different than other civs, but I think they are very nicely designed. Think outside the box and play to their strenghts, and they can be great.