As with anything I think this could be done as long as care is taken in balancing.  Honestly I like the idea of trading one resource for another as long as it is done in a reasonable manner.  The only real issue I see here is that using a high number of city squares doesn't really equate to a cost when food = more cities = more squares.  I am sure a balanced exchange rate can be found but I doubt they will do something like this until after 1.1 is released.  Perhaps after that point they will look at this sort of change.

The current system doesn't really stop spam anyway (unfortunately).  It is still just better to snatch all the food around and zerg cities.  I wish there was some kind of major bonus for focusing all your wealth/power/time in one or two cities.  Allowing people to trade one resource for another at carefully balanced rates wont really make city spam worse than it is already. 

i could support that idea... you can have food producing buildings, but only after you've built high-level cities like level 4 or 5 (not spammed ones).

I like the idea of mana/turn for food.  I mean the whole idea that the world is messed up and you are using elemental magic to fix it has a good feel to it to me.  Nice to be able to focus your magic on developing your nation.  Fits the lore well imo.

Maybe a high level spell to spend 200 mana or so to clone a food resource?

I agree with this mostly, however if we had a spell which took alot of mana to maintain that could create resources then it would actually push shards to being at least on equal footing with food sources as a limiting factor. Back in the dev diarys I have seen they were always saying how they felt shards should be the things everyone is mainly fighting over.

To be honest I don't mind things the way they are now... I am just saying if people want a way to create food then linking it to mana seems to be the smart way to go.

high end super spell ! 2000 mana cost! - spawn one fertile land !

its a poor people rich people thing.

huts - eat food to survive!
houses - fancy eating - (not being uncool and eat to much!)
villas (its all about looking skinny)

Gardens are in......

Can only build 1, costs 2 food, a good chunk of materials and pop. Need a level 3? city. It's not amazing, but it adds to a city that already has food, or provides a start point for cities without food nodes to start benefiting from improvements.

I think it's a decent way to go about it. You, in the end, can still get to "unlimited" food that way, you just have to re-research the top tier techs. I prefer that to spamming a building, spell, or whatever to get more food. Because the AI will abuse it, and people will complain.

Yup, it's in game as a L4 (I think) improvement; requires lots of people and costs 4g/turn to maintain, and provides 2 food.  Thanks, SD, this is what I wanted, a means to push a city up to L5.  Getting 13 food into a city (13 villas x 60 people = 780, L5 begins at 750) takes a bit of work, even with Nature's Bounty (+1), Granaries (25%), Irrigation (25%), starting with a fertile land (5), only gets you to 9 (5+1 x 1.5).  If you're lucky enough with Lost Bounty to get an orchard or bees nearby, you can get that up to 13 (5+3+1 x 1.5), but being able to add a garden means that now I can do this without luck (5+2+1 x 1.5); I just need to take a little food from another city that won't be going to L5.