I understand what you're trying to say, but that relies on the premise that what you are saying is correct, which it isn't...
Why is my premise not correct? Are there disadvantages other than the medium horse that apply only to lancers, and if so what are they?
firstly, lack of blocking, secondly, you underestimate the disadvantage that the medium horse brings when taken in conjunction with the lack of blocking, furthermore, lances are more difficult to aim than a sword, making things like jump kills something that are much less reliable, furthermore, a soft hit with a lance is much worse than a soft hit with a sword, given the animation time of a lance being heavily weighted towards the beginning, so you have over a second in which you can't do anything once your lance soft hits. Furthermore, you are much less likely to kill a horse in one hit with one hit with a lance, and the areas which do more damage like the head and belly are even more difficult to hit than with a sword when you consider the difficulty of the lance to aim. Furthermore, the lancer being extremely manouverable is a misconception brought about by the fact that the lancer can turn very far with the swing on the left side, which can be avoided by going on the right, and is not effective against multiple opponents since to get that manouverability you have to go quite slowly, and there for the falsely coined "manouverable" style of lancer play is incompatible with a team battle format. In addition, the couch is easier to fight than you think, since couching against a mounted requires sufficient predictive skills that not everyone has, and can also be out-ranged with a well timed swing. If you complain about being couched in the back, consider that you could be killed by a sword swing to the back also. Furthermore, there are effective techniques to deal with a slow couch if you are dismounted, which don't work 100% of the time, but neither does else, I'd even teach it to you to prove it, but that's something that i'm not willing to do prior to cnc since it wouldn't be fair for me to teach people ways to counter the irish team. Is that enough disadvantages for you? Since i seem to be able to get by by exploiting them.