When you define an object which is a member of SystemUsers group and which is persisted in LDAP, Aware IM pops up a dialog which lets you choose which attribute in LDAP will be responsible for holding the value of the access level. Aware IM will then take the access level value from that attribute. This will be, of course, within the context of the business space where you are defining the LDAP-persisted object.
I am not sure what you mean here by "different applications". If you mean different Aware IM business spaces, then there is no problem, because you will configure different LDAP objects for different business spaces.
If you mean the same Aware IM application running in a different business context, then you can solve the problem at the configuration level - for example, define a business rule that will attach a particular value for access level based on the business requirements of your application. You would still need to define an attribute in LDAP to hold this value, but this attribute conceptually will not "come from" LDAP, but rather be written there by your business rules.