Some form of steam-powered furnace? :S
I've seen concept arts of Fire/Water types, and once that stood out was a steam-powered squid-like machine thing (i'm sure some of you have seen it)
Politoed is obtainable (even thought the obtainables list says it isn't), but you can't get a Politoed with the ability Drizzle.
The main point of the pickup army is the Rare Candies which sell for $15000 each - that's where the real money comes in. I don't know how much you make from lower levelled Pickup Armies as I just went straight for 41-60 myself, but I can't imagine it's very much. But if you're still early in the game there's nothing you can really do about it.
Different levels drop different items. Lv 41-60 is the optimal if you want the Lucky Egg, but if you're going for high-end items (Rare Candies, Revives, etc) then Lv 71-100 would be best (you can get there using Rare Candies).