The proposal is just a routine application of known techniques . Research funding agencies are interested in funding research rather than development. Industry are expected to fund development work. The LINK scheme is appropriate for proposals which combine both research and development. If the development would benefit another research field, rather than industry, then look to the funding agencies of that field.
Industry ought to be doing it instead .
If no industry is interested then the prima facie assumption is that the product has no commercial value. There is no evidence that the proposers will succeed where others have failed . In this case, you should sketch the idea, and describe preliminary work you have done which shows that it is indeed a good idea. You are unlikely to get funding without such evidence. If you make it clear that it is an appendix, you won't usually fall foul of any length limits.