You have identified the basic problem; the MicroLogix cannot send a message to request a tag name directly.
The usual workaround is to use the "PLC/SLC Mapping" feature in the CompactLogix, in which the CompactLogix uses an INT or REAL array tag to emulate a SLC/MicroLogix style data table.
For example let's say we configured the CompactLogix to make Data File 7 match with INT[100] array tag named "IntegerFileSeven[100]".
When the MicroLogix requests "N7:10", it will get a reply with the value stored in "IntegerFileSeven[10]".
This feature must be configured offline in Studio 5000 Logix Designer.