you describe 2 different record layouts that reside within the same storage 
#1 - just a name
#2 - a name + a "transferred" property

depending on the situation you use either layout #1  or layout #2 for INSERT
reading might be OK for layout #2 in both cases.

Caché once had a somewhat similar sample with Person
and Employee extending Person. 
available here:
this Repo:

  • LOCK would be indeed the best equivalent to Isolation Modes
  • just IRISTEMP doesn't react to COMMIT or ROLLBACK  (there is no related Journal)
  • so instead of writing to your ^EVENT Global you may write to a PPG ^||EVENT acting as your  private temp
  • after Commit or Rollback you decide if you MERGE  ^||EVENT to public ^EVENT or not.
  • from your description, I assume you do it anyhow