Does anyone have any recommendations of what modifications to request to make it as uncomfortable as possible.

Why would you want it to be uncomfortable?

I think there is a difference between awkward and uncomfortable.

You can have an awkward appliance made for you that is comfortable and will create the effect you are looking for. Thicker acrylic on the palate will give you a bigger lisp and a tongue crib will do the same. Both can be comfortable.

Drooling is your body's response to having something in your mouth that it is not used to, and there isn't much you can do to change that.

You can ask them to install the expansion screw from a double feed plate. Than you will have the two spikes as an obstacle for your tongue….

Does anyone know if it’s possible to add hooks to be able to use a face mask with this appliance please?

Yes, you can add hooks on the canines on the upper plate