Maciek,
We are glad that you like the software.
Answers:
1. epesi uses adodb as a database abstraction library for PHP, therefore it should be possible to use MS SQL Server (both full version and Express) http://adodb.sourceforge.net/
We did not test it yet but since it works on MySQL and PostgreSQL we don't expect major issues with MS SQL. We will test this configuration in the near future.
2. epesi is based (in functionality, not architecture) on our other CRM solution that we used internally for several years. The scenario you described is not very common and this is why it is not implemented. While it is possible to rewrite the module to behave this way we do not plan to make this change.
However you can write a simple module that modifies the default behavior and get results you want.
