1. Publisher can chose not to have Steam DRM in their Steam version of game.
How many have done that, though? That's still overstepping their bounds. The consumer base doesn't want more DRM.
2. Steam version of non-steamworks game can easily be identical to retail version - it depends on choices made by developers and publishers.
You sure? Can you bring up examples of games that have actually done that without issue? Even if it is a choice, I haven't seen any cases of them doing that.
3. I often use beta patches for some of my steam games - without any problems. Poeple who are too stupid to appy patch correctly should let Steam handle it.
The build should be uniform, regardless. Steam should not be changing the product (even if they don't handle the multiplayer services or not). And are you using the beta patches through Steam or external ones?
4. Offline mode doent require any changes to game - if game need steam to be running, all you need is to switch to offline mode.
In the past, you had to download a good chunk of data to have games in offline mod. Either way put, you shouldn't need Steam to be run to play any game (save for Valve products that I expect to use Steamworks).
----------------------------------------------------------------------------------------------
This was touched on by another poster earlier, but, I forgot to mention how easy Steam can fuck up in their patching process. I've had it fubar too many times.