More about it here http://wiki.idempiere.org/en/IDempiere_workshop_2015/transcript#Promotions
Create plugin named org.idempiere.promotion. First Make this as separate Plugin and then apply logilite fix related to promotions
Yes, I think that's a good move. Using AD_ModelValidator does have its advantage - it can be make tenant configurable.
Triaged by Diego Ruiz,
I think it is still worth it to remove this from the core. Heng Sin worked in a ticket related to this not so long ago, where he removed many plugins from the core.