Advanced Tax Rules using existing fields

For stores that sell products that are sales tax exempt in some geographic regions and not others (for instance only batteries should be charged sales tax in some U.S. states), the current behavior of Tax Rules and Product Tax Classes is lacking.

For instance, if I want to assess sale tax on batteries but nothing else in State 1, I could give all my batteries a Product Tax Class called "collect tax in State 1" and attach it to my Tax Rules for every state, and then also attach my "regular taxable goods" Product Tax Class to my Tax Rules for every state EXCEPT State 1...but I would have to do something like this each time I need to introduce a new tax exemption state/product combination.

This quickly becomes hard to maintain, and becomes especially problematic if a second state later makes a similar law where only batteries should be charged sales tax...I would then have to make a new "collect tax in State 1 and State 2" Product Tax Class, attach that to all my Tax Rules, and then remove the "regular taxable goods" Product Tax Class from my Tax Rule for State 2.

I believe that adding the following two features would make it significantly easier for Zoey users to set up Tax Rules that account for tax-exempt products in specific geographic regions:

1) Allow more than one Product Tax Class to be assigned to a given product (e.g. batteries could be assigned both "regular taxable goods" and "collect tax in State 1" Product Tax Classes), and
2) Add a new field in Tax Rules that EXCLUDES specific Product Tax Classes from the rule and is prioritized above the INCLUDED Product Tax Classes (e.g. my Tax Rule for State 1 would include the "collect tax in State 1" Product Tax Class but exclude the "regular taxable goods" Product Tax Class.

Thank you for considering this request to handle more advanced Tax Rules.