If anything I think you are trying to over simplify it by pretending all these different groups you envisage will work together as fluidly as you say. We are having enough trouble with two partys working together...imagine trying to keep a rainbow coalition with 7-10 different partys involved, that is 7-10 party leaders, 7-10 chancellors, 7-10 groups of MPS, 7-10 grassroots supporters.
You need decisive leadership. Not more committees.
We have the current coalition in preference to an alternative 'rainbow' coalition.
It is obviously in the government's and the country's interest to form allegiances with as few other parties as possible.
The parties that refuse to consider compromise are left out of the equation and form the opposition.
Perhaps it's the sensible, mature parties that form those allegiances.
Remember the old adage, used to refer to Europe,: "we have to be in there to influence it. You can't influence it much if you're not part of it."