Ce-MLS makes an assumption (at least operationally) that there is a service which allows users to publish keypackages. These keypackages can then be accessed asynchronously, by group creators. Without it the bootstrapping problem needs to be solved in another manner.
Looks possible, but not efficient. A Logos storage can be used here.
This problem is analogous to X3DH Keybundles. In order to maintain asynchronous session initiation, the bundles need to be available to all clients. Status’ approach to this problem was to rebroadcast bundles every ~8-24 hours, so that the bundles are available to all members of the network. This has many considerable downsides.
My argument would be that storing these keypackages is much more efficient than the alternatives - though may require more upfront engineering.