Tool Control
The cutout and shaddow system is OK, if properly monitored by the PIC. The pilot follows the eng/mech on work by renewing his/her preflight after maintenance is performed, right? So, simply have this look include a backup look at the tool inventory.
This plan is only complete if it includes consumables. By this, I mean rolls of safetywire, etc. which are used on the job. Further, if there are tools out because they are broken prior to the job being initiated, their blanks should be noted to the PIC prior to job initiation.
This is not a end all silver bullet fix, but it is merely more eyes on an out of control system as it stands today. It likewise is not intended to be an insult to the the mech, but merely a cooperative effort to ensure professional, safe services to the passengers and service requesting agencies.