Your church needs to get a new group of engineers because what they are saying is not true. high ceilings do not force you to have to build a drum booth and isolate the drums.
If your church desire a booth the you need to have your building contractors to contact a studio builder to do proper sound reinforcement to the pulpit area and sanctuary. plexiglass alone is not the best option because it is too reflective.
the magazine Worship Facilities is what you should be reading. In it they cover all this and have listings for service people.
www.worshipfacilities.com and you can get a free subscription.
Aside from that contact Celebration Church in Nashville. The have a custom booth Built into their facility and can probably recommend their builder.