Out of curiousity what would be the effect of pitching at too high but dropping the temp over time? I know this is bad practice. I don't as much control over my beers as I would like right now due to a different location and brewing partner...long story...
Depends on how far it drops. Diacetyl would be my main concern if it was just a few degrees, but if it was a big drop the yeast could stall out early.
Let's say that the yeast was pitched at 70F and over two weeks the temp dropped to 62F. Is this a prime scenario for diacetyl? I am so used to using US05 that I am worried my practices will mess up the beer.
You just described my fermentation practice for the first 2 years I brewed. It's unpredictable how much that temperature swing will mess up your beer. My recommendation would be to just get it cooler before you pitch. If you can't chill the beer further, transfer it into your fermenter, then wait overnight. In the morning, the temperature will have dropped considerably and that is the time to aerate and pitch your yeast.
As for diacetyl with S-04 - I have never had that problem, but I always give my English-yeast beers plenty of extra time to clean up. I recommend you give the beer 2-3 weeks in primary, regardless of whether it appears "done" after 6 days. Basically, just give it a week longer than you would if you were using US-05. If you can't ramp it up to 70º F, at least you can give the yeast a longer amount of time to clean up after itself. In my experience, the extra week or two has caused zero problems, but "rush jobs" have caused me a lot of frustration.