I read this to be the use-case you're aiming to satisfy: (1) getting access to a range of exotics which are only available through certain providers in addition to (2) also getting the best rate available for all ccy pairs. I think this is currently provided by 'portals' like fxall and currenex (bloomberg now too I think) where majors competitively bid on quotes when they want to and the buyer buys that which best suits them.

There's a couple of problem with deliberate chaining of interbank trades in that if the market moves far you might not get your countertrade (the quote will be rejected on the trade attempt - it's more common for quotes to be non-guaranteed than for them to be guaranteed, presumably because it's easier to build and avoids the situation where hedge funds start gaming you); and - irrespective of that - prices tend to get naturally stale fairly quickly (every few seconds but it's usually inconsistent) which means that latency is a factor.