I've settled on Orchard as the new improvement for +food on Forest tiles. So as not to eclipse Farms, I'm adjusting the yield curve a little.
Base yield for Orchard will be +1 food, -1 production. So chopping a Forest to get a Farm, or building an Orchard, should give a near-equal yield.
Bonus yields lose 1 point of food, but gain back 1 point of production.
- Apple: +1 food, +1 production (net +2/+0/+0)
- Lemon: +1 production, +1 commerce (net +1/+0/+1)
- Olive: +1 production, +2 commerce (net +1/+0/+2)
Then the tech improvement curve is changed a little:
- +1 commerce with Currency (unchanged)
- +1 production with Invention -- this replaces +1 commerce from Crop Rotation
- +1 food with Organic Chemistry (unchanged)
- +1 commerce with Globalization (unchanged)
- +1 commerce with Genetics -- this replaces +1 food from Genetics, and ensures not losing food in the upgrade to Hybrid Forest
I can also give Orchards a chance to discover Apple/Lemon/Olives. Would any other resource be appropriate? There are several other resources that don't have a chance to be spawned by an improvement, but only Forest resources would be valid.