"If you would like more traders in your realm, come up with incentives and find out why people don't want to be traders. Don't lament to the realm, come up with a solution, that's your job as ruler or banker."
If I say to the realm, "We are having severe diplomatic issues and could really use a few Diplomats to help alleviate these issues. If you are willing to aid the realm in this capacity, please let the Council know so we can help coordinate your efforts." it sounds a lot like lamenting to me. In fact, mentioning any thing to the realm or individual players that involves "Unfortunately we need more of CLASS/UNIT" or anything equivalent is clearly prohibited.
At the same time, offering incentive is OK. So saying, "From now on Diplomats of the realm will be granted a place on the Privileged People Council and granted 500 gold at the start of their career. If you are already a Diplomat, let the Privileged People Council know and you will be granted this boon retroactively." seems completely in line.
Based on the guideline above, mentioning a need or desire (which can easily be taken as lamenting) is not cool. If it is okay to make such comments/request to a group of nobles, then the wording of that sentence, in my opinion, needs to be updated.