A year from now my clients are going to port a relatively complex intranet portal service (scheduling, actual tracking and reporting, and more) to Drupal because the head office says so. Very little effort has been made to determine if this is the right technical choice and it is beyond the control of my client's or even their bosses.
The current portal is an abomination that is in the process of being re-factored and I believe the most cost effective plan will be to bring in a domain model layer via Doctrine 2 and put 99.9% of all business & input validation logic into the models, gutting out the abomination until it is a skeletal view & authentication logic layer.
For any Drupal specialist out there, does this seem like a viable approach? Could Doctrine2 play nice with Drupal or does Drupal higher level logic need a much tighter integration to the data?