Although I would like to be able to use multiple checkers within Sigil, even if it means I would need JAVA installed, I realize it's easier said than done. However I find it important to mention the following.
All commercial ePUBs in the Netherlands are distributed through one single central institute who delivers the eBooks to various (big) online stores as well as Apple. They recently moved to a new version of ePUB checker. This means that all publishers - big and small - have to deliver epub files that are checked with the newer version of ePUB check. Regardless of any other checkers around, just to be sure.
Having said that, I wish there was a kind of compatibility checker around where one could check for the idiosyncrasies like the non-standard things one has to work around for Apple or the recent debacle with the new ADE.