I agree that it would be interesting to have such a open source SLES but you can only achieve this if you have a good community to make all these efforts.
Because it takes a lot of effort (very often with less or no honour). Afaik there are currently not many openSUSE (community) people interested in doing this. Although with the current opensuse build system it should become easier to make this possible.

If people are interested in making this open source SLES possible I'm always interested in joining that effort.