Having Ignition delete a column from a table because a tag is no longer being used in a Transaction Group would not be a good idea. Just because a tag is no longer being logged doesn’t mean that the previously logged data is not longer needed.
You don’t necessarily have to create 18 tables with 50 tags, you could create a long table something like -
id tagId value t_stampGranted it’s sometimes easier to whip up and work with a wide table, but I find there’s less maintenance with a long table.