While I think JeffE's answer is still the best and most generic, there is a second strategy to reinforcing your front lines: throw the best names in the field on the front lines, by using citations. I believe in citing heavily. First, it's good practice and great for cross-referencing later. Second, people you cite might be reviewing you if they're in any way relevant (so better make sure you're representing their main points right). Finally, it allows you to skip explaining things that others have already done a good job with.
Moe (2014), Larry (2015), and Curly et al. (2013; 2015) have indicated
that this a critical period for studying wolf dynamics, due to (timely
problem, such as tundra erosion in the Arctic) and advances in (your
method), which can identify key tipping points. These techniques can
not only reverse the decline of wolfpacks, but in fact introduce a new
world dominated by wolves, in a Planet of the Apes (Schaffner, 1968)
type scenario. A society of wolves will completely reshape how science in
wolfpack dynamics is conducted, enabling self-directed wolf research.
Well, maybe not the last couple. However, in total, that paragraph does the following rhetorical moves:
- Top people say: This is the time to solve Problem
- Problem + My New Method = Solution
- Solution => Broader Impacts
- Solution => Change in Research Practice
While you don't want to oversell, those are the main points you want to reinforce. Say them if you believe them and think others will consider them if you can back them up with sound methodology. In general, I would say introducing a research concept requires saying:
- Why it is important: What are the consequences? Why do we need more basket-weaving Maker Spaces? As a general rule, the more people it kills and the faster it kills them, the more money is spent on researching it (hence why rail guns and cancer medicine are both well-funded).
- What is the research impact (ceiling): How long have people been debating it? How much will it change how everyone does their research in the future?
- Why now: Why can we do it now, but it wasn't done before? Additionally, what makes you so special? Why can you do it but others won't/can't?
- What is the research impact (floor): Even if your approach fails miserably, what would be learned then?
You have the whole proposal to prove this (show, don't tell), but it's good to at least summarize a couple times in the proposal.