I can't directly answer your question except to say that anecdotally some people have found aikido safe and helpful.
What I will share is that there is an increasing body of evidence that says that many bulging discs will heal on their own and that there is not really correlation between back pain and disc abnormalities. It seems that various xrays and scans on people with symptoms show these bulges and herniations, so doctors jumped to the assumption they were causing the pain and other symptoms...but nobody was bothering to scan and compare over time people with/without abnormal scans and with/without pain.
I've been reading this intermittently in rehab and nursing journals for years and just the other wk there was a good roundup in the New York Times
. Apparently similar conclusions are being reached about meniscus tears and knee pain.