Bricks, Masonry, Asphalt and Concrete - Retrofitting Wood Deck with Brick Paver Surface

I have a 2nd story deck of wood-frame construction attached to my house. When it was designed, it was engineered to handle a dead load of 22 lb psf. The deck is currently covered with a dex-o-tec surface applied on top of the plywood sheeting put down on the wood structure of the deck. There is copper flashing around the entire perimeter edge of the deck.

The deck was engineered and constructed to eventually accommodate a brick paver surface [it just wasn't in the budget when we built it]. For instance, in addition to the engineered dead load, there is sufficient difference in elevation between the threshold of the door leading to the deck from the house and the deck surface itself so that the top of the brick pavers will still be below the elevation of the bottom of the door threshold (i.e. there is currently about a 3" drop between threshold and deck surface)

I now want to install the brick paver surface we had orginally planned [I still can't afford it - but what the heck!]. The questions I have that I would like some advice on are:

(1) what should I do about the existing dex-o-tec surface [remove it; leave it in place]? and

(2) What, if any, additional waterproofing should I apply [either to the top of the plywood when the dex-o-tec is exposed or right to the top of the existing dex-o-tec surface] before I lay down the mortar bed in which the brick pavers will be set?

Obvioulsy, any other input or advice would be greatly appreciated.

Thanks very much.

The brick alone, not counting mortar or existing structure is a dead load of around 18 psf.

I'm most likely using 1/2 width brick - although my engineer told me that full brick + mortar would equal 22 lb psf.