Can you expand on the problem, it's not clear.
How many user defined labels do you have? Is system multi or single tenant?
If multi tenant and you've got a link between LIRU and the tenant record (and you don't have hundreds upon hundreds of custom labels, could you not just place a shortcut as the label text
Eg
Label = loggedInRegularUser.obTenant.Form1_atteibute1
The only proviso is that it becomes something else to drag around in SQL calls. Alternatives can be to set it as a string into the LIRU or the LIRUSessionVariables either whenever it is changed by the Tenant (Business rule IF Changed then find all Tenant Regular Users and change attribute) or when the Regular User logs in.
Finding the labelsBO and keeping the context is probably going to be a PITA if there are multiple customisable attributes per form and you find them all, how does the label know which of the way 5 Labels to use? I am guessing that the EDIT action as the last action signals the end of the operation and uses the default display logic.