Needed more.. (contains spoilers)
Ultimately, I guess what they needed was more money, because most of the intersecting plot lines didn't have enough screen time to develop. The only portion of this story I found plausible was the relationship that evolved between Joseph and Isabel. Several key points I felt were rushed or presumed prematurely, probably due in large part to trying to fit the movie into as small a container as possible.
1) Joe and Danny had an almost believable relationship, but there wasn't enough "human" interaction there to support the idea that they were close. There needed to be more scenes like the one where they're drinking, and Joe accidentally made a mess all over himself while he was opening his beer. They seemed to be laughing together in that scene. Maybe their relationship didn't come off right because most of the movie was spent either exploiting Joe, or talking about exploiting him (albeit somewhat begrudgingly on Danny's part).
2) The Gangster starts off as plausible, but quickly becomes confusing. What thug who will kill a man over a 10K debt, is going to continually give money to said indebted person? The man who was willing to kill, suddenly has a soft spot? Why? One would believe that a man who has made his way to living in a penthouse, would be able to outsmart the tragically dimwitted Joe, in the event that Danny proves to be less than useful. Needing more money would make him a burden, so this doesn't make any sense. Men like that don't play games.
3) The relationship between Danny and Lisa escalated rather quickly nearing the end, and I don't think the audience had enough to go on to believe it. Sure, she's an aging prostitute without any prospects, I get that, but she had her art, and presumably a dealer who was at least casually interested. It's conceivable that she COULD go somewhere with that. I think what their story needed was a non-sexual scene where we would be able to see them bond over something simple. Cue the right music as they discover something small they like in one another, and I'm hooked; I'd buy it. I felt like that's where the story was headed when she came by for "her knickers and keys" (clearly there was some latent feelings she had that were about to be explored), but then the story shifted.
4) Deano saving Joe from Curtis at the end didn't really add up. Quite frankly, it would have been more plausible that Joe should die or be seriously injured there, than the ending that transpired shortly thereafter. Curtis was clearly higher up the food chain, and murdering him would most certainly have repercussions if discovered. Even if they got away with it, Deano cared so little about Joe that he wouldn't pay his way with Danny when he initially offered Danny a job, so why save him? After all, he had just beaten Deano's fighter for a costly sum. It just doesn't square up. It's as if they said, "Well, we can't kill Danny, the audience will hate us for killing a retard.. so what do we do here?"
5) The ending to me is just ridiculous. We've come this far, why kill him? Okay, kill him, but then transition the soundtrack into an upbeat melody after a 20 second somber "he’s dying" piece? WHAT is going on here? I have a feeling that the blood that trickled out of his mouth was digitally added later when the "head-slump" wasn't telling enough. Aside from that, what about the consequences his death would bring to the other characters? Danny was the glue that held the whole house of cards together, even as loosely as he did. Without him, forget it. We're asked to believe there was this great burgeoning love between Lisa and Danny, which MIGHT have supported the idea she'd care for the "children", but if you remove Danny and you have zero realistic potential for her to care for Joe and Isabel. Why would she? She barely knew Danny, and has no obligation to care for his life-partner/brother or his girlfriend.
If we had to accept the movie as it was presented, they should have allowed Danny to live. Sometimes people need to die in the end to give their character more meaning, but his death did nothing to further this story. Had they given Danny a real opportunity to show us he wasn't just an addict who makes horrible choices, his death may have been tragic like they probably intended. It just came off as a cheap attempt to pull at people's emotions, especially when they followed it with that credit music. The exploitation was just too obvious.
This isn't a movie you can say, "Well it's a movie, what do you expect?" There were no over-the-top special effects or truly out-there plot concepts I take issue with, so it's not allowed that card. Also, this is supposed to be loosely based off of "Mice and Men". For those who've read that, perhaps the elements of the film that I took issue with made more sense. Assuming the audience has read the source material isn't a very good idea, even if you make it glaringly obvious. You still need to use some mechanism to clue the audience in to what is going on in the story, so that we know what is truly motivating the characters to do seemingly unbelievable things. They did neither with this film.
All things considered, I enjoyed the film; however, the story deserved more time to really gain traction from its moving parts. They chose to substitute character and story development for "Drama for the sake of Drama". Hopefully a Director's Cut comes out with the scenes that are sorely missed in "Best Laid Plans".