Hmm, even it is a less critical or non-production system: downtime might be acceptable, data loss never. That's why probably none of your customers is using a RAID 0 array
So a UPS is an essential part of any open-e installation. I would prefer if this would be much more highlighted on your website, especially for the "NAS in 10 minutes" kind of customers.
There are even hardware suppliers offering complete server configurations based on open-e software and do not even offer any UPS system listed on your compatibility matrix...