Thank you for mentioning Capsula Mundi, good to learn about their practice of burying the body in a biodegradable pod as contrasted by the cremated remains in a urn.  
Have you surveyed the public yet on their reaction to your vertical garden idea?  I'm interested in reviewing the results if you are willing to share.

Music does have amazing power with people near end of life.  I recently had the amazing experience of being sung to by the "Threshold Choir" who sang beautiful harmonies while I lay in a chair simulating a patient.  Very moving and powerful experience for me and several others who had a chance to lay in the chair and hear the choir sing to them too.  Patients facing end of life who receive live music from skilled performers are especially blessed while others who hear recorded music played experience similar benefits too. 

Love the idea of dying outside, under a tree, surrounded by nature.  What a seemingly nice alternative to dying indoors!