correct me if I am wrong, as I get it, your question is about modifying the USR05 directly without going through application, correct?
Options:
Help from ABAP developer with simple BDC program on SU10 will suffice for your requirements.
Benefit:
1. standard way, should be safe even with changing of release or support package.
2. trail looks good, not modifying the SAP tables directly.
Disadvantage:
needs ABAP knowledge and a bit overhead in processing.
ST05 trace when doing SU01 to get what you want to know, then proceed with your current idea:
Benefit:
loading is faster.
Disadvantage:
1. not safe, current conclusion may not applied for the next release or SP( change of code ).
2. directly modifying SAP table without going through application level or SAP Notes instruction is generally a bad idea. not sure about the audit opinion if this get tracked.
IMHO, the first is better, less trouble in the future 
GUI Scripting is also a possible option if it is enabled in your system.