I think that trying to use GW rules for 40K to play a truly competitive game is like building your house out of dung. You can do it but you will always be wondering about that smell. Games Workshop says their games are not designed for competitive play and it is a hobby but then they sponsor events like Hard Boyz. Their statements about competitive play is more of an intentional cop out so they do not have to care about making it a fair competition between the armies.
The problem is of course the rules. You cannot play a game competitive unless everyone knows and understands the rules. Beyond just confusing and unclear wording in the rules, the whole structure of the rules is insufficiently organized. In a game driven by special rules you would expect definitions of categories so that rules can be quickly and clear defined. You can create a hierarchy of how to apply them to cut down on all the problems. In a properly formed system, no one would have to write a 100+ FAQ to try to cover any marginally reasonable question people could ask. Those people who put in a ton of work get bashed for it by haters on the blogosphere. The haters either think their answers are obvious, they give the wrong answer(so such answer must not be obvious), or they have a gone so far as to admit to changing the rules. It is not like GW does not change the rules in their FAQ, they just do not have the balls to admit that is what they are doing. Remember Errata and FAQ are different. In an Errata they can rewrite the rules but a FAQ is only supposed to clarify vague issues. I am all for changing some unclear or obvious against intention rules. I would probably support a lot more rules changes and think it could go a long way to making the game more competitive.
Of course GW does update the main rules on a consistant bases now. Looks like every 4 years going forward, but they do not do this to tweak the rules to make the game more balanced and rules more clear. It is purely a planned obsolence system to make money not to make the game better. While every army would love to get regular update some lanquish for so long that they really do not allow their use in the uber competitive ultra optimized list world. Watch out when your army does get updated. You might all the sudden have an illegal army with no HQs. (I am not kidding, my nids lost their warriors and Broodlord as HQ choices so I had no HQ in my 1000 points anymore). Or you find that they have made your current models overcosted with new units that are better in most ways and less costly in points so that they can sell their new plastic kits.
Currently you have the codexes that are just not good enough or have a single build which appears. People who want competitive gaming should be working on getting these list fixes as part of their event FAQ. I am sure all the out of play armies could be brought into line with some point adjustments and some subtle use of current USRs. The game would be a lot more competitive if you had to worry about facing 16 different codexes of armies on a level playing field. A competitive game should be about who is the best at the game not whose collection matches best with what GW has decided is going to be the best armies right now or who is willing to just throw money at GW for that current army. Finding that unit that GW has improperly priced and bringing as many as you can should not be where the competition should be. People always defend this unit spamming as building redundancy and real armies have multiple repeated units. This reminds me of an saying, "You go to war with the army you have, not the army you want."
Fixing the game as an event organizer is a ton of work and you would probably get flak from it from all circles but your ideas would be more useful than debating a single elimination or swiss format. Now if a real competitve movement starts, the work can be shared with a rules and balance committee made up of organizers of the events signing on for annual review cycle. You get 4-6 large events using the same rules/balance packet and you are probably in business.
I would think that if you really want to test your skills as a commander, the events should use prescribed lists. Some mirror battles would be interesting to see who can out move and out fight his opponents. It would probably been limited to the main armies like space marines or now IG since you would need to have the army people have selected to play. Or give them a realistic force to build their strike force out of with limits on the items in the forces armory. This takes a good part of the hobby of picking and building your force up out of the equation but might be interesting secondary events.
Now I am sure this editorial can be ripped apart. If it was published on BOLS it would be ridiculed in a rainbow of colors but the main point is: If you want to make it a competitive game you need to do the work to make the rules clear and the armies balanced, GW has made it clear that they have no interest in doing it for you.