In Dwarf Fortress 0.31.12, Elven diplomats incorrectly arrived with the caravan (as if they were a liaison), gave the Dwarven greeting, proposed a tree cutting quota, then departed with the Dwarven farewell message. When version 0.31.13 fixed this, it also completely eliminated tree cutting quotas from the game. I did an experiment with a fortress in 0.31.14 and I've found that it's possible to bring them back, complete with the behavior they were supposed to follow all along.
Edit raw/objects/entity_default.txt, locate the position definition for RANGER_CAPTAIN, then copy/paste the following code directly below it:
[POSITION:DIPLOMAT]
[NAME:Diplomat:Diplomats]
[NUMBER:1]
[RESPONSIBILITY:MAKE_INTRODUCTIONS]
[RESPONSIBILITY:MAKE_PEACE_AGREEMENTS]
[RESPONSIBILITY:MAKE_TOPIC_AGREEMENTS]
[APPOINTED_BY:DRUID]
[PRECEDENCE:70]
[DO_NOT_CULL]
[COLOR:7:0:1]
[MENIAL_WORK_EXEMPTION]
[SLEEP_PRETENSION]
[PUNISHMENT_EXEMPTION]
[ACCOUNT_EXEMPT]
[DUTY_BOUND]
Once your Baron(ess) is appointed, a Diplomat will silently arrive at the beginning of the next Spring, scold you for your tree cutting (or congratulate you for not cutting down any trees), then leave. Every year afterwards, an elven Diplomat will arrive about a week after the caravan shows up (or possibly during the next season if a siege showed up first) and propose a tree cutting quota, exactly like they did back in 0.28.181.40d and earlier. Even better, if the Diplomat manages to get killed, a new one will be appointed the following year (in fact, due to the "new liaison every year" bug, you'll get a new diplomat every year whether they live or die).
The exact same code (minus the "[APPOINTED_BY:DRUID]" line) can also be added to the Human entity raws (right after the WARRIOR definition) in order to make them send a regular Diplomat instead of their Law-giver (which might be a demon that emits deadly fumes) which should also be replaced each year (whereas the Law-giver's additional responsibilities seemingly makes it ineligible for automatic replacement).
Do note that these changes must be applied prior to world generation.