Gavin Andresen - 2014-10-17 16:02:17

...basically the blocks just contain the txids - which can be matched with those in each nodes memory pool (assuming they are present - they may need to "request" txs if they don't already know about them).

I think you're reinventing Matt's fast block relay code.  See:
  https://bitcoinfoundation.org/2014/08/a-bitcoin-backbone/