I am 7 yrs out from having had an acute form of GBS. I too have residual damage. My most excellent Neuro told me last week that at times when you might wonder whether things are starting up again symptom-wise d that that is NOT the case. It is because of the damage done to the nerves muscles from the GBS which may prove to be permanent.
That said, it isn't to say you can't regain function again. You just might not be able to realistically get back to the level you had before the GBS hit you.
No idea what sort of Rehab you had a year ago but most Insurers won't cover Rehab for an indefinite time period. Intermittent evals are a different story though as long as it can be medically justified and directed by an MD.
Have you tried any Pool based exercise classes in the area where you live? Being in water is very soothing and you can actually float a bit so you aren't weight bearing all the time. These classes also use balls for specific exercises so you may want to give that a try. Check around in your community to see what might be available.
Don't Not try golf which at least is less physically demanding than racquetball to sort with. Try it and see. I would even suggest trying a Mini Golf place to start and see how you do as its not only your legs but your arms, your hips (twisting motion with a club swing) and eye/hand coordination etc that are also involved.
Your exercise tolerance for past sports you enjoyed doing is going to be waaay down in the beginning. Expect it. The difference is Don't Try to muscle through (pardon the expression!) doing it for the sake of. Damage to the nerves and muscles to some degree more likely than not has occurred. If you push as you used to be able to you could well end up in a World of Hurt . Try going for therapeutic massages, focusing on your problem areas- the muscles in your legs and those that support the hip.
I also noticed very recently I have a leg length discrepancy as identified to me by the Massage Therapist I go to see once/week. It is caused because my muscles are extremely tight such that it is pulling my hips and spine out of correct anatomical alignment. Is something like this also happening to you? I had never had that before either and I am 7 yrs out so was very surprised my Chiro and Massage Therapist both pointed it out. Luckily, they can both help adjust it as well via specific stretching they do that I can't involving the affected leg.
I also strongly suggest you try finding a good Chiropractor who is experienced working with muscles and joints (mine is outstanding and also actively provides Sports Rehab level chiropractic services as well). I know Chiros in general have a less than sterling reputation as so many seem to be pretty useless but don't give up as there really are good ones out there that can offer relief and suggestions to try. Keep trying. If anyone you know is involved in semi pro or pro sports, ask them what Chiro or PT person they go to see. That's the expertise level that will undoubtedly help you the most.
I too have times when my balance is "off" and I have to be really careful so as not to fall and injure myself. It was only in the past 2 yrs that I began noticing the warning signs that such an episode was heading my way that means I have to take greater care in walking etc. Depending on the degree of damage you might have, take note of what happens immediately prior to your balance being off, assuming it isn't off on a full time basis. All the more reason to periodically get checked by a PT and a Chiro as well I may add.
Do NOT over stress yourself physically. Acknowledge you had GBS and depending on how incapacitating it was for you, realize it has very possibly changed the degree of physical stress you can subject your body to now. That is just the way it is. If your balance is an ongoing issue and its been a while since you last had a PT eval, consider asking your MD to direct one now. Do you need to use a cane to prevent against falling? Do you need more supportive shoes with custom orthotics to help with balance, you might want to see a Podiatrist to have your feet evaluated assuming an Xray of the feet that your MD can easily order for you can rule out any visible structural issues.
Everyone recovers at different speeds. Depends on the degree of damage done. What does your Neuro say based on his/her most recent exam findings? It takes time to recover from the insult GBS slammed you with. You may or may not get back to the state you were in before the GBS hit like a runaway freight train. On the other hand, there may well be room for improvement but you might be better served if you were evaluated properly first. PTs do work with patients that have balance issues too and can teach you things to try or do that might also help.
Stay strong and know there are a lot of us out there that understand exactly what you are saying.
Best wishes for a continued positive recovery (even if its baby steps).