Are there different custom-fields for each record?
How do you know the fieldtype of each custom-field?
Can you post a print_r of some example-records with its custom-fields?
Did you had a moment to check my reply?
I was thinking live editing in a mixgdb grid can help solve this situation too
Does joined fields can be presented in the form as updatable values using for example ContentProperties_property_value?
What are your suggestions?