If the crimps are made off properly, what will the soldering achieve?
If your concerns are around vibration, then soldering can reduce mechanical stability of a multi-stranded cable termination by "wicking" up the conductor and losing your flexibility - this may also increase volt-drop and cause other problems.
With lead/tin solder, migration of the elements in the solder over time because of pressure at the termination causes a problem; the situation is different with modern lead-free solders, but still a consideration.
EUR ING Graham Kenyon CEng MIET TechIOSH
Principal and Proprietor,
G Kenyon Technology