Add charge credits functionality for dropdown multiple field - charge for every choosen item from list

WHY IT USEFUL
The main monetize basis of RSDirectory! is a charge credits for the fields.
But imagine you have a list, for example service "translate to languages" what contains 100 languages.
Now it can be solved only if create a checkbox group with single field for EVERY language.
It requires 100 additional custom fields what makes a big size of MySQL #__rsdirectory_entries_custom table.
It also have a bulky view at frontend EDIT interface with 100 checkbox extra fields.
And it all is heavy to load just because of quantity of the extra fields.

Instead of that it would be great to have a single dropdown field where for every choosen item RSDirectory! adds a defined credit amount.
For example if a translation for item cost 2 credits - user has choosen 5 languages from dropdown list - and it charges him 10 credits accordingly.

IMHO it's a good improvement for RSDirectory! functionality.
Thanks in advance for attention to this Feature request.

Best regards,
Serge