[Alan in AZ]

I think simple is good. However for convenience add some kind of connector clips for the battery connections, your inline fuseholder (I recommend the ATC/ATO types - easiest insertion & color codes). I'd also add a push switch so you can make your connections then easily apply power as needed. Some connector probe clip options for the connection to your equipment under test and even an indicator light after the switch so you know you are applying power and have not blown the fuse...

Still pretty simple - but more functional & convenient.

Alan