Bonus with N territories for N armies is too strong
This is worth elaborating on. Bonus efficiency, safe capture, coverage, etc., play a big part in introducing strategy into the game.
Imagine a map with 600 bonuses all of which are 4:4- on standard settings (0% SR, 2 neutrals, Random Warlords distribution), any one of those bonuses can be quickly captured (usually in 1 turn, even at the start, depending on the warlord position) to recoup all 4 armies spent conquering the bonus (2 neutrals kill 1 army) the very next turn. This makes that map very friendly to expansion. You'll either have a bunch of picks (for coverage), making the game tedious and hard to reason about, or you'll wind up having games decided just by who got luckier after picks and had more room to expand.
You want room for expansion but not too much. You ideally want some parts of the map that are better to pick than others, although swinging too far in this direction creates "pick lotteries"- situations where a player wins just by getting an obviously better-than-everything-else starting position after picks, off of luck. Common ways to achieve this strategy element to maps include keeping maps small, having bonuses vary in efficiency (so players can predict rather than blindly guess their opponents' possible positions), having bonuses vary in safety (e.g , position relative to other efficient bonuses, hard-to-defend borders), having bonuses vary in internal shape (for example, East US and Australia on Modified Medium Earth both are 5:6 but Australia is a less connected graph and so has more common warlords that can't capture the bonus in 2 turns), and having bonuses be less than perfectly efficient (a starting rule of thumb is N+1 or N+2 territories for N income, depending on how easy you want to make expansion on your map- note that this creates virtuous cycles).
Of course, those are just suggestions and you can and should experiment with your mapmaking. Don't have to build for strat either, although casuals still reward templates with strategic merit because those are also more fun to play on.
