1) In my opinion, some type of players should comment/vote on their type of suggestions.
E.G. Team League/Tournament suggestions should be voted and commented by people that participate in leagues and tournaments with their teams, since all others won't understand it properly for sure.
2) It is also very important not to make guidelines like 30 votes, 95% and so on, simply because not every suggestion can achieve those guidelines. - competitive suggestions have rarely ever reached even 15 votes, as they get overrun by PUB suggestions, while even get few T_DOWNS from people that don't see a need for it.
(e.g. I don't play with team, therefore i don't see a need to increase map size for this)
That system with votes and % was also bad in DA forums, as people were calling each other to support their suggestions, and they would support theirs in return. (simply it was more like political battle then actual place for posting suggestions)
For example, I had 2 suggestions in DA forums that were later on introduced in DotA in a similar way, but both of them were nowhere near achieving 30+ votes or some high T-UP percentage, therefore that voting/potential mechanism was clearly very bad.
3) Mods should have more active roll in selecting and improving promising suggestions, and it might be good to even have specialized mods for all sorts of DotA suggestions.
For example, 3-4 mods specialized in competitive suggestions, 10 mods specialized in cosmetic suggestions, 10 mods specialized in hero suggestions, and so on.
In that system, 1 or 2 mods could see a good suggestion, and recommend it to other mods of that type for analysis. If 3-4 mods of same type find it usable and feasible, they could recommend it to IceFrog directly.
OFC, if some suggestion would get some high user output, it would definitely call moderators to check it, but I also believe that those specialized mods should at least check every thread of their sort.
For example, they could put some sign visible only for mods, that would say that mod has checked the thread and mb even his vote, so other mods could skip that thread if they dislike title or vote, and so on...
Mods votes could be something like this:
1 - unnecessary suggestion
1-4 - poorly written, solid suggestion
3 - even at its peak, that suggestion lacks
3-5 - suggestion has lots of potential, but it needs to be improved.
5 - bull's eye suggestion, other mods of a sort check it ASAP.
E.G. first number representing current suggestion status, and second number representing its potential. (1-1, 3-3, 5-5, might also be represented as 1,3 and 5)