Rules: How Flexible is too Flexible?

Taking some inspiration from Brom's amazingly unloved DARK AGE: FEUDAL LORDS ccg (man, was that REALLY 14 years ago?!), the Tripods Trilogy, and Cormac McCarthy's _The Road_, I started my own post-apocalypse board game experiment. There's also a little touch of the Dvorak card game in the deck that goes with.

The map itself is cubes, with up to six players, color-coded by "Gangs." In less than six-player, one color is neutral to show that the space isn't controlled/owned. Control is done in patterns by the cards played after combat. As I'm still formallizing the rules, I'll skip big details for now, in lieu of the crux of my post.

As I started the rules document, I realised I had a ton of places for variability, namely:

1) The board itself. Using cubes like this, you can do standard squares and rectangles, sure, but also could adapt the board into things like maps of Manhattan or Paris, coneceivably. In fact, I've added an item in the rules that you can expand the board itself (the game is planned for 20 cubes in the box itself) by using d6, and substituing colors for the pips/numbers on the d6 for colors on the cubes.

2) Winning, part 1. I've included 5 base victory conditions that players would agree to to run the game as scenario based (land grab, "capture the flag," last man standing, victory points, and victory points to win a set number of turns). Even in this, though, I think you could leave it up to the players deciding on # points to play to, turns to complete, etc.

3) Winning, part 2: There is also a mechanic I've toyed with called Motivation, where the Gang bosses in the game (the PCs) choose a motivation card as the game begins that allow them a separate alternative victory condition. I'm planning on 12 such cards (each gang having a choice of 2). These would be more set in stone.

I guess that's it. Man, I thought there was more I was worried about.

Anyway, I don't know that the game needs to be dungeon-crawl in feel per se, and in the game's deck there are lots of instant effects (it's 200 cards; the Dvorak esthetic of "thing" or "action" comes into play here for everything from weapons, to how you control land, etc.) which will also allow the game to evolve and change up between plays.

There are a few other things I need to decide on, but they're minor.

So here's the question: in those three areas above, how much should I say "THIS IS HOW I WANT IT" versus "Here's a few suggestions; play how you like" in the rules? Also, could all this indecision be sidestepped by doing BOTH: an introduction rules set that sets everything in stone and an advanced set that allows all the flexibility?