My comments:
1. Use marines, ghosts tanks and firebats, don't use air units.
2. Make the map look like a "base" very open, lots of paths to go places, not just one little thing.
3. Creep WOULD look good on this because of what you are trying to do, make bases that are covered in slimy crep would be fine.
4. Make human bases surrounded by zerg, then when you finally crack through those zerg, you get the base and are able to purchase some extra units and regain your health.
5. Make sure there are plenty of dead guys on the walls (use the doodads)
6. Make the base realistic, you can always make dead buildings the use a trigger to lower the hp of the buildings to make them burn when a unit comes near them.
Answers to the questsions:
1. Twisted.. p1 a builder is kidna stupid.
2. Teleporters:
Condition:
unit A enters location A
Action:
move all unit A's at location A to location B
3. The grenade trigger (this might b a big complicated)
This requires 3 players minimum (one neutral player)
Condition:
player A steps on location "throw grenade"
player A has 1 grenade at location "grenade stocking area"
Action:
Remove 1 grenad efrom location "grenade stocking area"
Create 1 scourge at location "player A hero unit" for player B (neutral player)
set switch 1
preserve
Condition:
Player B has 1 scourge at "player A hero unit"
switch 1 is set
Action:
Center location "grenade" on scourge at "player A hero unit" (grenade must be atleast 6x6 size)
clear switch 1
set switch 2
preserve
Condition:
Player B brings 1 scourge to "grenade"
Player C (enemy) brings 1 unit to "grenade"
switch 2 is set
Action:
center "grenade" on unit owned by Player B at "grenade"
order scourge to move to "grenade"
clear switch 2
set switch 3
preserve
Condition:
player B brings 1 scourge to location "grenade"
switch 3 is set
Actions:
wait 1000-3000 (you can choose the wait time)
remove 1 scourge from "grenade"
Create 10 wraiths at "grenade"
Kill all wraiths at "grenade"
kill all enemies at "grenade" (all is in a matter of speaking, you can change it so that the grenade doesn't destroy whole masses of enemys, or have it kill 6 or 7, and set the hp of the rest to 1%, whateve ryou want)
clear switch 3
preserve
if you didn't understand i can explain each step later on.
4. Not possible to stop creep, not posible to stop zerg health regain sry.
This is possible: (if you want "levels" of enemy units, set the max hp for a zergling to say.. 5000, then in each area of the map, have it set the hp to something different for example)
Condition:
player 1 brings unit to "portion A"
Actions:
set hp of all units at portion a for player C to 30%
DON'T PRESERVE THIS TRIGGER.
all for now i have other stuff i need to do.