Survival games are fun, working on one myself actually... nobody steal my name (Or main ideas including skins, units, etc...)
I loved playing Ice Troll Tribes, yea jungle trolls and island were fun (Jungle was by far the best) but Ice Troll made sense, why would you be frozen in a jungle

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Anyways, as for suggestions. Have a variety of units, but keep the
ingrediants (If using recipe system like troll tribes) simple, instead of Pig Skin, just keep it skin. Sure you can make bigger animals drop larger quantities, but make better buildings require more. Have some more rare items though.
I suggest you have an option for teams, I absolutely HATE the fact that troll tribes was ever player vs player, it wasnt designed for that at all. Not only was the map to big, your already fighting against enough and if a guy dies they leave, thier team is to small so they leave, you win, its over.
Another idea, make animals wander around (Not just using wander ability, thats just periodic sidestepping) make them actually attack-move to other side of the map! You can steal the boss idea from Jungle Troll Tribes, just make there be more, and instead of camping in the corner make then wander as well.
Make the creeps get harder over time, and have some type of hostile AI that just likes to attack you for no reason (Hell make it the ice trolls LOL that would be funny)
USE A BACKPACK/EXTENDED INVENTORY SYSTEM!
I HATE HATE HATE how jungle trolls had so many armor and weapon types when you needed the extra 1 space to stack! (In my map when you right-click an item ill make you walk to it then add it if your inventory is full [If i can get it working, probrably possible])
Stacking? Yes, limits on each item should probrably be listed (Or take it to the max and make strength increase carrying limit of some items

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EDIT: Oh yeah about the drainie, people player single player all the time. I personally cant stand it! I HATE the fact that people are only working on lame AoS's and single player RPGS! Thats why Wc3 is losing so many people... There used to be all kinds of maps, arenas, td's, misc games like who wants to be a millionaire, survival games, footies (Still a bunch i know)... the list goes on and on, untill today. Now its just 3/5 DotA, 1/5 ... (CHAOS/UTV [Dam korean maps shouldnt be allowed on USWest/East!]), the rest is usually footmen/td's that are PROz ONLY (Most which are just completely idiotic or imbalanced to the max)... Jesus I went off track ok Im done.