Whats the correct way to allow different jdbc drivers for deployed applications on JBoss / Wildfly?

My setting is the following:

I got an application, which I deploy in /standalone/deployments
The jboss-deployment-structure.xml of my deployment in /standalone/deployments looks the following:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure>
    <deployment>
        <dependencies>
            [...]
            <module name="org.postgresql"/>
        </dependencies>
    </deployment>
</jboss-deployment-structure>

To drop the jboss-deployment-structure.xml completely (because it must not be used if there are no classloading issues), doesn't work. I use more dependencies (keycloak) beside the driver, which can't be found then.
My module.xml in my module org/postgresql/main looks like this (like described in https://www.keycloak.org/docs/4.8/server_installation/index.html#package-the-jdbc-driver)

<?xml version="1.0" encoding="UTF-8"?>
<module name="org.postgresql" xmlns="urn:jboss:module:1.5">
    <resources>
        <resource-root path="postgresql-42.2.5.jar"/>
    </resources>
    <dependencies>
        <module name="javax.api"/>
        <module name="javax.transaction.api"/>
    </dependencies>
</module>

My requirement is, to allow different types of jdbc-drivers, e.g. postgres, oracle, mssql.

First option:

I can change my jboss-deployment-structure.xml to

<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure>
    <deployment>
        <dependencies>
            [...]
            <module name="org.postgresql" optional="TRUE"/>
            <module name="com.oracle.ojdbc6" optional="TRUE"/>
            [...]
        </dependencies>
    </deployment>
</jboss-deployment-structure>

(added the optional-parameter)

Then I have to allow all drivers explicitly. Seems to be not the best way.

The idea comes from the standard documentation.

Second option:

I change my module-path to driver/jdbc/main (instead of org/postgres/main) and the module.xml to

<module name="driver.jdbc" xmlns="urn:jboss:module:1.5">
[...]
</module>

(changed name of module)

and go with the module-reference in my jboss-deployment-structure.xml like

<jboss-deployment-structure>
    [...]
    <module name="driver.jdbc"/>
    [...]
</jboss-deployment-structure>

Now I force my customers to name the driver-module like I proposed. They can't name the module like mentioned in every standard-documentation.

The idea comes from this question.

I am doing this in context of a keycloak installation with a self-implemented User-federation to access a separate (legacy) user-database. Therefore dropping the jboss-deployment-structure.xml is no option as mentioned above.

Whats the correct way to achieve my goal of being flexible with the jdbc-driver?

EDIT: mentioned, dropping jboss-deployment-structure.xml is not working.

Solution

At least I went with a hybrid solution of my two above mentioned approaches for the jboss-deployment-structure.xml like as follows

<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure>
    <deployment>
        <dependencies>
            <module name="org.postgresql" optional="TRUE"/>
            <module name="com.oracle.ojdbc6" optional="TRUE"/>
            [...]
            <module name="driver.jdbc" optional="TRUE"/>
        </dependencies>
    </deployment>
</jboss-deployment-structure>

I listed all the relevant database divers as optional modules and listed another one with flexible naming if a driver is desired, which is not mentioned in the list above.