Date index for Mar 2003

Hello all,
sorry for the newbie question, but I'd like
to have some additional fields in the customer entity
(essentially, another phone number, a tax code and
a province code).

AFAIK, the way to do this is:
1. in SQL, do some alter table add... stuff
2. hack class.customer.inc file (and related, if needed)

Of course this kind of work will broken
itself when I'll upgrade the system with the
next new (latest and greatest) achievo release.

I'm wandering what's the planned pattern
to handle this kind of situation (if any).

Any help will be useful.

TIA
/gp

p.s.: a (weak) suggestion, only to discuss:
add a customer_additional_parameters table with
id foreign key(customer.id), param_name, param_type, param_value
(marshalled to string) and modify the base atkNode class
to handle such a situation).