If I move the fermenter upstairs wouldn't the temperature rise be too fast? It would go from 50 to 65 in a few hours.
No, that wouldn't be a problem. With my last Helles I employed a maturation rest at 72F for 3 days before I crashed it to 32 F.
My experience, however, has been that I rarely need the diacetyl/maturation rest for diacetyl reduction but for reaching the targeted FG. After fermenting the beer at 46-48 F for 2 weeks I don't notice diacacetyl. Only a sulfury note.
At what wort temperature do you pitch the yeast?
Diacetyl has never been a problem in my lagers but I can not (and this is probably a lack of skill because traditional commercial producers do it) get the best attenuation without ramping up. This makes excellent lagers reliably.
On the issue of substituting ale yeast for lager yeast, I've been thinking about doing the opposite and making an IPA with lager fermentation (I know this is not a new idea) based on having the Mikkeller yeast series where I thought that what the Chico yeast does for hoppy beers (get out of the way of the hops) the lager yeast did much better.