My preference is for multiple units to be used in synergy.
Module for external repairs (hull and screen) something like a slime repair system, a bit like a semi transparent expanding foam that's pumped over / into the hole / defect and sets. When used on fractured windscreen partially obscures vision. System can be powered down when not in use. No effect on repair cost as slime needs to be removed and repaired. Slowly repairs hull and ship needs to be stationary to allow foam to set correctly. - medium weight / low power consumption.
Module for internal repairs (all internal systems, including thrusters and FSD) involves rerouting systems electronically to backup systems, must be left powered on to have effect. No effect on repair cost as original system needs to be repaired and restored from backup. Takes time to initialise - Low weight / medium power consumption.
Proactive maintenance unit - when utilised with above systems to negate / reduce wear and tear by rerouting damaged electronics or filling hull micro fractures prior to them becoming a problem.
I was going to post something similar.
Enhance the existing AFPU to also fix thrusters (still using ammo).
Add an new Hull Repair Unit to fix hull and make it use (certain) metals than can either be mined or taken along as cargo.