Let's see, government's are usually differenced by: number of rulers, election process of the rulers, dimension of private property, dimension of civil rights. Which of those dimensions do you want to represent as governments, and which as policies?
As an example: if people speak about communism, they usually talk about Stalin style communism. Thus in reality they talk about a despotic (one ruler, or a very small cliqué), bureaucratic (promotion through success in a bureaucratic system, and not via elections), state-capitalist (everything is owned by the state, not by private owners or by "all") system with extremely limited civil rights.
If you go for all 4 dimensions, with only 3 possibilities per dimension, you'd have to come up with 3^4 = 81 governments. Some of them haven't even been tried yet I suppose. If you go for less dimensions, you significantly lower the amount of possible governments. To give you an idea how such a dimensioned system could look like:
# of rulers:
One Ruler (very small group) - Minority - Majority
choice of rulers:
Inheritance - Bureaucracy - Elections
Private Property:
"Communism" - Regulated - Neo-Liberalism
Civil Rights:
Authoritarian - Regulated - Libertarian
Now remember that I only assumed 3 discrete points for each dimension, which is much to low for a good description. But it's a start, and might give you ideas. To give you examples, here the last 100 years of german governments (and from those examples you'll see how bad 3 discrete points are, but why simple categories are worse):
The Kaiser: One Ruler, Inheritance, Regulated, Authoritarian -> Monarchy
Weimar Republic: Majority, Elections, Neo-Liberalism, Authoritarian -> Democracy
3rd Reich: One Ruler, Elections (moved to Bureaucracy), Regulated, Authoritarian -> Despotism
early BRD: Majority, Elections, Regulated, Authoritarian -> Democracy
DDR: Minority, Bureaucracy, Communism, Regulated -> "Communism"
late BRD: Majority, Elections, Neo-Liberalism, Regulated (moving slowly to Libertarian) -> Democracy
The categories are so broad, that the same category "democracy" can mean Weimar Republic, Adenauer and todays Germany, which where significantly different in both questions of private property as well as civil rights.
The simplest would be of course to just go along the "who rules, and how are they choosen" path. But then neither Communism nor Fascism have a place as governments. So for me it would be up to the question: which dimensions, and how many discreets do I want.