We have a branch ("multiple-web-servers") where this issue is resolved in an another way; the docs are still lacking but code is working; this branch will be merged in "default" very soon - I hope you will like it.
Yes I noticed afterward. I am currently working on the "multiple web-servers" branch too, planning to add support for flask, supervisor and gunicorn.
BTW, I don't know if it is a bug or if you are using an other version of fabric-taskset but WebProject method _expose_to(module_obj) return a generator, not a list. I couldn't test with the VMs yet as my updated OS X broke VirtualBox badly.