What is your estimate of the amount of work needed to create a minimum usable version of this extension? If the answer is "a month's worth of Sunday afternoons

What is your estimate of the amount of work needed to create a minimum usable version of this extension? If the answer is "a month's worth of Sunday afternoons to make it work, plus about double that to make it polished", then it is definitely worth pursuing, even if the only benefit you would get would be some name recognition on your resume. If the answer is "a year of development by a mid-size team of highly skilled developers" then it seems very unlikely to me that you will be able to bring such a project to completion, much less make it profitable.