Criticism is important, as it acts as a kind of quality control here, and we are striving to make this game the best it can be. Every idea is definitely not going to work, and even many good ideas wouldn't fit into the game, in light of overall themes, other things in the game, etc.
Shadow, sometimes you do tend to come off a bit abrasive, though, but I suppose that's your choice :s
Just to be upfront, though, I dislike the idea of another town. You're suggesting that there are numerous shops there, and other towns will have shops, what are all these people going to sell?
Secondly, this side quest doesn't seem like a lot of fun to me. Go to these towns, and find people willing to do stuff for a Deku king. Dunno, can't explain it very well, but it doesn't sound like the kind of thing I enjoy. This is a personal preference, though, so my sole opinion isn't super valid.
Third, having an entire town develop is kind of HUGE for a side quest. Thing about side quests is that they have to be... On the side. An entire town developing is a big deal, and kind of undermines the focus of the game, particularly as it doesn't relate to any of the game's themes.
Not relating to any of the games themes, or tying into any plot or personal details is another thing. This side quest doesn't relate to the rich vs poor theme, or any sort of oppression theme, which is kind of recurrent here. It doesn't really relate to the Deku people's problem or personality, and doesn't relate to any specific NPCs, really, in terms of resolving conflicts of theirs.
Sorry to be so harsh, but it doesn't seem to me like it has too much to do with anything :/