Can you provide more informations on this issue? Some test cases, oracle error messages, oracle settings..
You are proposing to remove the double quotes from DROP TABLE statements. You can turn identifier quoting on and off. When you have ATTR_QUOTE_IDENTIFIERS to on, all your identifier names are double quoted in oracle and if you do something like
SELECT * FROM user_tables, the TABLE_NAME column contains table names lovercased. So you need the double quotes in DROP TABLE statements. If your table name is "my_table" and you do DROP TABLE my_table; you get an error about nonexistent table. You need to do DROP TABLE "my_table". That's exactly what doctrine does now.
Another scenario is doublequotes turned off. So all your tables are handled in oracle uppercased. So my_table is internally handled as MY_TABLE. That's alredy what you recieve from USER_TABLES. And when you do DROP TABLE "MY_TABLE" that is the same as DROP TABLE my_table.
I use this heavily in both cases and I have no problems with that.
The issue with I.SEQUENCE_OWNER in DROP SEQUENCE statement I fixed in r6896 (http://trac.doctrine-project.org/changeset/6896).