Going totally low end would have killed Blackberry even faster IMO.
Blackberry DID stand a chance against both iOS and Android, because they preceded them by quite a bit. The problem with Blackberry is they just assumed their model was correct, and when rumours surfaced that Apple would produce a touchscreen slab phone with no buttons, they just laughed. And then they said even if it could be done, the product would suck because of battery life issues, etc.
Then Apple released the iPhone and caught them totally off guard, and then AFTER that Blackberry got serious about it, but by that time they were too late, because this stuff takes years to develop.
Reports are that BB10 is actually pretty decent, but it was simply several years too late. If they had put their resources into this years prior, then they could be a big competitor.
BTW, whenever I picked up a Blackberry in the early 2000s, I always thought it sucked. It just floored me that they couldn't come up with something better... and nobody else could either, because it didn't take a UI designer to realize that the UI need some serious updating. Mind you I was looking at it as a consumer, but it seemed like the consumer market was almost an afterthought for them. They were far too wrapped up in only the corporate market, and then threw out a few crappy consumer market to see what stuck.