Hello,
Coming up with a concrete list of suggestions is hard, but here are a couple things that would make it easier for me to understand large proposals (e.g., like the linear types one):
1. It is good if large proposals are "modular", meaning that you can understand them (and perhaps implement them), one piece at a time. For example, adding certain features to the language may enable us to make library changes, but that sort of thing can be disused separately.
2. I think that it would be good if the proposal contains enough information to get a feeling for the core idea of the proposal, both how it might be used, and about how it might be implemented, without referring to external papers. One thing that works well for me is to see lots of examples which illustrate various aspects of the design. Generally, I find it much easier to understand and generalize from a set of examples, than a set of rules, especially if the rules are not accompanied by an explanation of the reasons for choosing them.
-Iavor