Hiding issue fields for some users /user groups

We are planing to invite our customers to post feature requests and defects about our software.
Right now, i can add only one field layout scheme to a project and all users will see all fields of this scheme. It makes no sense, e.g. that the customer can set a fix version, he should not be able to do so, as he does not know.
I would suggest a general solution, to avoid the discussion for every field.

1. Solution: A issue field security level (smiliar to issue security level)- For each field a security level is applicable. Only those fields are visible for the user group, that are a member of this issue field security level. Users/ user groups not a member of this security level will not see this field (the field is hid)

2. minor Solution: More detailed permissions for the system fields: e.g. "Set fixed version", "set component": not having the permission will not allow me to edit the fields (as is already implemented for assigning users)

3. Solution: create a master layout scheme for the project.
create a sub layout scheme on user group level. each user will see only the fields of their user group, even though all fields exit in the database. Some user groups may then see more fields than others.

In order not to generate errors with required fields, it should
be possible to set default values for all system fields (not just custom fields): e.g. default value for component=unknown, fix version=unkown.

maybe this issue could be solved by the requirement of adding a general customer object.