Manage drupal's form (and nodes) from external pages

I need to manage drupal's forms (and nodes) from external pages: there's a D6 installation AND a working site with a custom framework (that invoke drupal_bootstrap for a full API access).
Many pages are managed in D6, but presented on the existing site (full transition to D may will happen in the future, but not now): this is relative easy for "simple" nodes, but more complex for forms.

I've already set a solution to use custom login and registration box and pages (retrieving form fields with a snippet built as a custom - modified - version of drupal_get_form) but I'm looking for new ideas on how to improve it. Any advice welcome.