Then perhaps, if the absolute guarantee of implementation is definitely off the table, participants are incentivised by other rewards. There's still worth in holding a crowdsourcing event of this nature - it would generate a pool of ideas that wouldn't have been generated otherwise (without the event + incentives).

We don't know, there could be a few small and easy-to-implement great ideas that are received, so the possibility (rather than guarantee) of implementation would be on the table. I do see that offering a 'guarantee' of implementation could be a bit reckless.