Re: Suwari Waza
Try to spend some time each day just sitting in seiza. back straight, good posture. As a "westerner" who didn't grow up using seiza as a regular seated posture, it will never be as comfortable for you (me too) as someone who, growing up in Japan, has lived it in his/her culture. I understand that modern Japan sees seiza less frequently used - I wonder if that's causing "westernization" of their knees?...
Hakama do cost - if you get the really fancy indigo-dyed cotton hakama, you'll wear through the knees fairly quickly. If you get the less expensive "Techron" (whatever that is) from, say, Tozando, they'll last longer, dye won't run, and you can even buy hakama with relatively permanent pleats. Wearing hakama for suwari-waza makes it easier on your knees because the gi pants and the hakama material tend to slip against each other more easily than your knees (especially when sweaty) and cotton pants slip over the material of the mats.
I found that when in dojo that let/required us to wear hakama my knees fared better. And yes, when the shihan decides to go on a 20 minute rant about how yudansha are expected to protect partners and mudansha and to pass on the best aikido we can, the knees HURT and the legs don't work that well for a few moments after getting back up.