Let me describe a use case. We have zabbix[history*] items, but we discourage using them because they can produce huge load on the database. On the other hand there is a relatively lightweight zabbix[wcache,values,<mode>], usually used with Change per second preprocessing option. If we could add another preprocessing step (let's call it Integral or Cumulative) to add current change per second times time since previous check to the previous value, we would get same result as zabbix[history*] plus some constant.

From time to time (after housekeeping and/or new partition creation) item configuration can be changed to zabbix[history*] and back to reset deviation to zero.