Improving Database performance on custom fields

Currently, the system supports two types of custom fields: Radio Buttons for yes/no, which create tinyint boolean fields and all others, which are varchar(255). MySQL is significantly more efficient in searching integer fields and it is wasteful to use 255 bytes for something that is really a single character field. When defining custom fields, it would be desireable if it were possible to define that they are expected to be numeric and to also be able to define the length.