Last night I published an update to my OpenTTD NewGRF called Tea Tea Deluxe. Version 1.2.0, downloadable from the "Check online content" menu in the game.
I've played the game with these changes for a couple of weeks now, and the improvements are very enjoyable. The production rates for the farms is now a little bit higher. Increased from 8 to 12, compared to 15 for coal, which actually makes tea leaves somewhat competitive. They start out at a higher value than coal but drop off radically, whereas coal loses value very slowly. For short distances tea leaves are more valuable, for medium to long distances coal is the winner. For the longest distances, when value of any cargo has dropped to the lowest point at 12% of its maximum, tea leaves are quite superior. I didn't intend to make it this way, but it's how it turned out.
The probability of construction of farms has also been tweaked. Again I've compared it to coal mines and set the probabilities for construction at map generation and during gameplay to the same values.
It's always tempting to make your own production NewGRF better than all the base industries. I didn't want to fall into that trap. I did want tea (the secondary product) to be a bit of a luxury product, however, and I think I achieved that by having value for the leaves drop steeply.
Let me know what you think of the NewGRF and whether anything should be tweaked, changed, added, or removed. I'm open to any and all suggestions!
-- CC0 Björn Wärmedal