@EasyTrieve There has been talk since at least 2013 that HSQLDB will be replaced by Firebird for embedded databases. It is available to test in later versions of LO.
I tried it a while back with LO ver. 5.0.2.2. I quickly found a problem in creating auto-increment fields. The GUI in creating a Table with an auto-increment field appears to work but after saving the Table and opening it in Edit mode it does not have it as auto-increment. Looking at the documentation for Firebird I found that it does not implement auto-increment fields directly. You have to create a Trigger to do so. After creating a Table with an auto-increment field it is necessary to use SQL to create the Trigger. Opening the Table and putting data in the Table produces a confusing result as every record added shows the auto-increment field as 0 until you close the table and open it again when the correct auto-increment values are shown. The same happens if you use a Form to input data - you need to close and open the form again for the correct values to be shown. I don’t know if this has been improved in later LO versions. With HSQLDB the Database directory in the .odb zip file has a script containing the SQL to create tables and includes the creation of auto-increment fields. With Firebird there is just a single firebird.fdb file.
UPDATE 4/3/2017
I can confirm that the auto-increment problem I mentioned above has been fixed in version 5.3 of LO.