I have posted some thoughts here and there, and finally decided to put all my thoughts on supply issues into one post. So here goes:
1a. First of all we don't like micro management, so no need for any supply units (on
land that is, I'll come to that). They would only make a slow game in the later stages even slower. Roads/RR are more than enough to keep your cities and units supplied. Road/RR supply would also cause the neat side effect that you
can't do this unrealistic dash with a warrior or scout the first thing you do, who is able to cover the entire continent AND keep your capital updated with a fresh map of its findings over thousands of years. You can't venture too far or you'll fall out of supply. Settlers would have to be supply sources of their own, since they would consist of roughly as many different types of people as in a city (which is a supply source), after all that's what they are there for, founding a city. This would also mean that an escorting unit following a settler would also be supplied.
1b. As a little side note, you should obviously be able to transfer food the way you like between connected cities. If you have one of those remote desert cities that are just there for the need to connect other cities and potentially bring you future resources like saltpeter or oil, you should obviously be able to send them food from say a city that has reached Pop 6 and lacks an aqueduct or river.
2a. An
unsupplied unit is a unit that isn't on or
adjacent to a tile with a road/RR connecting to your supply source, which could preferably be one of two cities that are connected to each other, friendly or
neutral (unless this particular neutral has some sort of agreement with your enemy or another reason not to help you), not
enemy. More ideas on supply sources could obviously be discussed. This would also have a neat side effect, namely the unrealistic stack combat we see. My main problem with Civ warfare is how it forces you to attack cities, which in reality is what you can and want to avoid. You wanna try to go around and cut its supply lines, since a city is often much easier to defend than open ground.
2b. An unsupplied unit loses 1 hp/turn. When down to nothing it is eliminated. There are ways to supply them from the outside (which I'm discussing further down), allowing them to
maintain their strength, not
heal.
Guerillas should take longer to wear down, maybe they'd lose 1 hp every
two turns instead or something. An unsupplied
city is not able to produce and would slowly starve. As a side note, I do though wish to stress that I agree with the people saying that a bombarded/starved city/metropolis should retain its defensive bonus.
2c. An idea that might seem a bit complicated goes like this: Unsupplied units don't cost any upkeep as long as they are unsupplied. Their upkeep is kept in a special upkeep pool. If they are saved from their trap and back in supply,
half their upkeep for the time unsupplied is paid, the rest goes to your treasury. This is because you wouldn't have to give them food or ammo when unsupplied (unless you do as in points 4a, 4b and 5, which would be handled in a different way), but they'd still want to be paid for their work when back in safety. If a unit is eliminated, the total upkeep for the number of turns unsupplied goes directly to your treasury.
3. Enemy roads (not
railroads, though) are usable, but you
cannot attack in the same turn as you use them. You would have to state whether you wish to use the road or not. If you don't use it, feel free to attack if in range. If you do use it, you can't even fortify in that turn. The roads only provide supply if you control them (if you were the last one to use them, the game would have to remember and you could have a function where you could see which part of which road was under which side's control, if you'd lose track on it). Once you
control a railroad, you'd obviously get to use it as well.
4a. In my opinion,
naval supply (and trade) should work differently. This was something I stated in another thread and has a lot to do with making your navy count for more than being just funny toys. You should have to have
Merchant Ships to keep an island supplied. These would obviously be vulnerable and in need of escort. You could potentially use transports, but merchant ships would be much cheaper (also making you less worried about their necessity gameplay wise). This way, you'd be able to load a ship with supplies and send it to a coastal city that is cut off from land supply (see 2b), also making naval blockades less abstract. These ideas are, though, more about giving the navy a more realistic role than it has now. The main purpose of navies (apart from offshore bombardment and troop movement) is to protect or attack supply ships, that's why I want merchant ships but not the old land caravans from Civ 1 or Civ 2.
4b. A costal city that receives naval supply should be able to act as a supply source for the rest of the island or your (or a neutral's) part of that continent, depending on how much it receives. How to balance this could be a matter of discussion/calculation. I'll not be bothered at this stage.
5. Another idea concerning 2b and the question of supplying units that have been cut off is that of
air supply. Have a bomber make a normal bombing run, except instead of dropping bombs it can drop supplies. The drop can fail (misdropped) or be intercepted (through fighters on air superiority). If the drop is successful, the tile it drops on does
not act as a temporary supply
source for that turn, but the units on or moved to the tile itself are temporarily supplied
for that turn. What should be needed to keep units supplied according to points 4a, 4b and 5 then? Well, possibly 1 food + 1 shield/tile (and possibly/probably the number of units in there) you try to supply, temporarily taken from a supplied city of your choice (you could obviously take the food from one city and the shield from another). This would simulate dropping rations, ammo, clothes etc into the unsupplied tile.
There you are, hope the rest of you are as fanatic about supply issues as I am.
! This would give you the PROPER effect of a supply-line-most importantly, a line you can sever to leave units stranded in enemy territory, a more historical movement rate, particularly within your own territory (and especially in the earliest ages) and, best of all, it does it without introducing yet another unit to manage!! Anyway, if you want to learn more about supply lines and operational range, check out the following threads:
