Custom table options in professional

Hi, 

Your professional version should include custom table options or a way to just pay for additional features, I don't need any of the Time tracking, Sales integration or anything else that's included in the business version but it would be good to add custom columns to allow me to better filter the tasks and Gantt charts.

With your current system, I would have to spend an extra 80$ a month just for this feature.

Cheers