Separating the two connector halves is going to be the best way to make a proper repair.
BMW rarely soldered terminal connectors to the wires. Instead, a double-crimp was used whereby the first crimp rolled a portion of the metal connector over and onto the wire. The second crimp did the same thing but grabbed tight to the wire insulation. These connections resisted, to a degree, the damage that might occur earlier with a rigid, soldered connection.
To determine if you need a male or female terminal, the connector must be separated.
You mentioned the terminal for this wire is long gone. The raw end of the wire may have failed do to corrosion, excessive flexing, or a ham-fisted PO. The terminals usually stay in the blocks. Let's just blame the PO for this.
Your local electronics store -we call 'em Radio Shack 'round here- should have a terminal to suit. That's another reason to pull the connector apart; you need to know the correct size. The new terminal does not have to be the double-crimp style but it must fit its male or female counterpart. If all you can find are terminals with the plastic bits, cut off the plastic as it obviously ain't gonna fit into the block.
Couple points: The terminal connectors are held within the connector blocks by a small tang that goes in easy. To remove a terminal, use a very small flat-blade screwdriver to locate and depress the tang while you gently pull the terminal clear. Refit is cake.
While at the store, pick up a small tube of dielectric grease and treat every terminal you come across with a light smear. Prevents corrosion. Insures good electrical performance. Battery terminals also love this stuff. There is also a spray can product of terminal cleaner that will not damage plastic nor paint. Good to use as you can shoot some into a connector block and see gunk drip onto your shop towel. Using both products can add years of performance to your circuit's life.
Fix it proper and fugitaboudit. Hope this helps you to "see the light".
