Didn't there used to be an option to add the url of a more appropriate forum for a question to be asked in? What is the procedure for suggesting a more appropriate forum? If there is not an option to provide a suggestion for a more appropriate one, it would be a useful feature. For example, in the dialogue box where the option for meta.philosophy.stackexchange.com appears, there could be a text entry box to select after pasting in the suggested url.
This question has been answered on the general Meta SE:
The list of sites is limited because many people who vote to migrate do not fully understand the scope of the target site, or migrate questions that are of marginal quality, so many questions get migrated when they shouldn't be. [...] Moderators do have this capability. If you do not have this capability in your "close as off topic" dialog, flag the question for moderator attention, with a comment specifying which site the question should be moved to, and we will migrate it if it is appropriate to do so.