I don't want to propose any solutions because I don't understand what the source of the friction truly is. If you understand the real sources of friction, could you explain it in some more depth?
I sense that the lack of contribution to the codebase is because it's inconvenient, not necessarily difficult. It seems that it's inconvenient for the reasons you said: 1) the reddit fork is hard to modify and 2) the site owners are reluctant to change.
But I also sense that the proposed features aren't too difficult to implement (because they're relatively common) and that a handful of skilled volunteers could get it done in a few weeks (very rough estimate; I'm way too inexperienced to really say, but I do sense that it's very doable). Perhaps it wouldn't be compatible with the reddit codebase and it'd take a major overhaul.
But I really think the benefits would outweigh the costs. The costs would be a few weeks of a handful of programmers' time (or something like that, I don't really know). The benefits would be huge! Imagine LW users collaborating on new projects, brainstorming new ideas, contributing to and benefiting from the list of life hacks, studying together, having hack-a-thons, rooming together, having more productive discussions, summarizing the content to make it more accessible to common people etc. etc. Isn't that worth a few weeks of time from a handful of people? Even if only one or two projects emerged from the site overhaul, I think the benefits would outweigh the costs.
Sorry if my argument for why the benefits outweigh the costs isn't concrete enough. I tried.
I admire your optimism and determination. It's not my intention to convince you not to try. Even if you don't succeed, and it's not impossible that you could succeed, you will certainly get a lot out of it. So take my negativity as a challenge, and prove me wrong :).
I think it'd be a good idea to keep a list of the ways we'd like to see LessWrong improve, sorted by popularity. Ie. email alerts for new responses.
So if you have an idea for how LessWrong could be better, post it in the comments. As people up/downvote, we'll get a sense for what the consensus opinions are.
I think there's a pretty good amount to be gained by improving LessWrong.
Note: I say "ways to improve" instead of "features" because "ways to improve" is more general.