The changes for TBaseModel are in the svn now. It did not even have an custom create.

E.g. now you can do:
[pascal]
Model1 := TBaseModel.Create(nil);
Model1.LoadFromFile('models\tulip.3ds');
Model1.SaveToFile('tulip.txt');
Model1.Free;
[/pascal]

If you need advice on how to write your own descendant from TBaseModel let me know.