only allow things to be recalled if they have been on the market a certain amount of time, say 6-8 hours or somthing

I don't like it.

1) A safety click for the recall button.
2) Lengthen the time goods are back on the market.
We have the recall feature now, and it'd be much more fun to play the market games over 72+6hrs waiting period. Goods being stuck on the market longer will make recall be used more and have a tactical use. 48+4 is just too short, and just crashes the market.
3) Increase standing orders for each type of good.
Three isn't enough. I'd like to see 5 for techs and military, and 12 for supplies.
4) Maybe eventually a recall that can select one type.
Maybe make it cost two turns. One would still be too cheap, as this is a pretty powerful ability.