Way I see it, the "I'll nominate Heskey" scenario isn't going to happen here in any shape or form. Nobody will be interested in a player who has been nominated PURELY as a ruse.
What might happen here is that people will nominate players who deserve to be in the relevant category and who might be of interest to them - but they won't break down in tears if someone else gets them. That's the worst case scenario, if you will. Most people will nominate a player they indend to get.
Making it a non-bid deal allows for the possibility of certain neutrals to nominate players in a scenario where there's a dearth of good options - which could plausibly happen down the line, when people start to get their teams together and aren't desperate for players.
If you go for the nominations - as opposed to just let people bid freely for whomever they want - I think this is the best way to go.
I retain final say in nominations so any shenanigans like nominating Heskey won't be allowed.