I see as well too many problems with this idea! First of all I would suggest to use Warlight Forum search for quite a lot similar topics that mapmakers shoud be rewarded something - might even be a uservoice for this.
As Min34 pointed out maps quantity over quality! I think this is already a problem? Most of the maps are not exactly played really often.
Second from Warlight Wiki
Players can earn points by winning multi-player games or tournaments, unlocking achievements, or from ladders. Points are used to gain levels, which unlock additional features.
So my question is why are the points important? What they give in real terms. If you want to open achievement the thats why the Lottery games were created - takes 1-2 days to open all unlockables. Same goes for achievements - i have never even looked what I have or not nor anyones else - I do not see point of this. If one plays for points, achievements then probably I would diagnose a repetitive feedback complex - or something similar it is called. I have always hoped warlight would not turn into those another addictive game-styles to keep some players playing, because they cant find meaning nor sense in their doings. (Just for a side note: it is rather odd to see world treating all kind of addictions, put leaving one of biggest trends on 21th century kill its youth).
If something were to be given to map-makers then. As posted on previous threads-posts, it must be something more valuable. For example choose every season a best map (either all submissions or particual theme contest) - and give maybe coins or even a membership. I think a method of that would be more welcome, because it will easily wipe out the quantity issue. Second 3 or 4 months is decent period to perfect one map - although for larger maps and people who have less time in hand it might take even longer as for me. After all I do not think most of the maps made deserve some price at all. Or just for every DECENT map made (let the Fizzer or somekind of community to decide) would give player a small amount of coins. Yes, inflation is the problem, but it helps Fizzer to promote Coin games and raise the playerbase as well (in this place I would assume players who play with coins know the system of Micro-finance and game-money inflation theory - I hope I did not violate any rules by pointing it out).
My advive to promote quality map making would be simple: 4-Times a year Full Theme Contest. Fizzers makes the Contest: Players are given 3-4 months to submit. And either Fizzer or Community would decide for the best map and some are given prices. (Maybe 1th to get membership others some coins etc). And for outside-contest small prices, grants as well to promote it.
* The same idea works on Guides as well. I think warlight lacks guides: Map-Maping, Template-Making and so on for gameplay. If Fizzer would announce best Guide-maker for each category would receive something - then probably there would exist one already!