noSQL Shema Management

I have a few ideas to improve DBAL and ORM management for php:
1. Reading if needed ORM schemas definitions from YAML(existing plugin)
2. Then migration it into the one of NoSQL databases(such as MongoDB or Memcache/MemcacheDB)
3. Creating transactional temporary-changes data layer in NoSQL for a current-changes due the webapp launch and running for each run
4. Periodically migrations of a current changes with migration script into RDB(for example by cron)

So we get:
Fast automatic shemas management(Symphony users - I say you "haha" because you have to do some unuseful things like "doctrine:build-schema" etc)
All advantages of RDB (like JOINS) in a data extraction
Full-independence in data changing due to webapp launch(and no transactions are needed) in the current NoSQL data-layer
Low load to the server because after extration we have a lazy return data into the RDB
In feature a simple caching any fast-changed data into NoSQL

What do you thinking about it?