The gentleman who managed summer reading here last year said that the prior developer had not included "delete an organization" functionality because it was complex and required changing too many database tables. If the tenant stuff is anything like the rest of the database, I suspect that there may not be foreign key constraints so it will be challenging to figure out exactly where in the application related tenant data is stored or referenced. Just removing the organization record and seeing which parts of the GRA work and which parts do not work sounds like quite a journey down the rabbit hole.
Unfortunately, between getting our winter reading program running and now preparing for our summer reading program, this issue has not reached the top of my priority list. I am hoping to address it for the 4.0 release which I hope is going to happen in the fall.