Nanban: Sounds like a great idea! Sorry I can't offer any advice about how to do this but having read your posts, I admire your tenacity and resourcefulness and have every confidence that you will be able to figure out a way.
I, too, have been banned from seeing my GD. Sadly, I have also contributed to this situation. Three years ago my OH was undergoing treatment for cancer and we were staring into the abyss. Into this darkness came the news that my S and his OH were expecting a baby. The news bought us hope and so it proved to be.
GD was beautiful and I fell in love with her! For two years I babysat weekly while mum went to work. She found motherhood difficult (who doesn't!) and their lives were chaotic, filthy cold house, baby not fed etc, etc. I bit my tongue but I guess my disapproval showed.
S experienced mental health problems and couldn't cope and I had several frantic phone requests for help while he was caring on his own (while mum was at work). I took them all on holiday for a short break to try and give some support and respite. I eventually took over washing GD's nappies (cloth - she wouldn't let me buy disposables) as mum didn't soak nor wash any for 2 days and didn't change her frequently enough with resulting soreness and extreme discomfort for GD. Frankly, as we were in shared holiday accommodation, the aroma of steaming nappies gave a ripe ambience!
The situation further deteriorated when we returned home. S's OH was increasingly jealous of my relationship with GD who would cry and cling to me when I took her home after babysitting. I would make excuses to mum saying she had just woken up etc, in order to attempt to limit the damage to mum's self esteem.
Mum began venting her ire, posting inappropriate content about me on social networking sites. I had a word with S to make it stop as it was increasingly embarrassing as well as compromising my professional position. The situation deteriorated, we had a row and she said she didn't trust me and I would not be able to see my GD again. Since then she and S have made a couple of very tentative approaches at reconciliation but I have ignored these.
Using your child as a weapon is inexcusable in my book. If I did re-establish contact, I fear future manipulation of a similar sort if/when I next upset her. I also find it painful to see my GD continue to experience what I consider to be inadequate parenting (although this has improved marginally).
I'm not proud of my actions and I suspect that my disapproval of their life choices will prevent this situation from ever being resolved but life is too short to spend it in the company of people that cause me such distress. My OH is in remission and has some limited contact with them and takes GD presents, Easter eggs etc. Sometimes he is allowed to bring GD to see me and I cherish these times.
I appreciate that my stubbornness is to the detriment of that gorgeous little girl and this remains my regret.