I think more slots are a bad idea, as it gives the power-blocs within CN more chance at winning CN:T every time as they can simply pile-on the smaller alliances, thus any competitiveness will be taken out unless you join such blocs. Indeed, we would end up seeing a progression towards the giant blocs who already hold sway in CN. For these reasons alone, unlimited slots are a terrible idea. Unlimited war slots would mean CN:T would simply become a massive mess of bloc vs. bloc. In such circumstances, any victor would likely be due to chance rather than strategy or knowledge of the game.
If people want to war at the moment, they already have a total of six slots to do so, with the maximum attacking slots being three. This number, I feel, keeps such competitiveness and also provides an adequate platform for any war-monger's appetite. There is no need to adjust the current system.