Yes I get the idea, and have been thinking about the same. Such a feature would have to be in the consensus algorithm in order to avoid two of the orders to be filled simultaneously. Another possibility would be to go fractional reserve on some UIA, but then you would need to be the issuer.

One more possibility for adding liquidity would be to visually combine orderbooks in the GUI. For instance if you want to exchange MAID to STORJ, the software would calculate routes over different pairs, like MAID->USD->STORJ, and include that virtual order in the available orders. Then, when excecuted, the software would secretly make two orders in the separate markets, and the user would get his STORJ.

These, however, aren't a part of this Worker Proposal. This WP is about liquidity bot software.