Interested to see if anyone can critique my multi-purpose brick pit design here, and answer a few questions.  I've built something close to this in the past using cinder blocks and learned a lot that I want to incorporate into the new design.  I'll explain the design, and questions after, please comment if you have any suggestions.... Thanks :)

Purposes of design:

A. Direct pit BBQ, where the logs are burned in the fireplace on the left (which is elevated) and has a rebar/metal cage at about 30" height on which to burn the fire and let the coals drop through to be collected and shoveled into the front door on the left side smoking chamber.  This is meant to replicate the burn barrel/direct pit NC-style BBQ.

B. Indirect smoker, using a top loading (steel lid) brick firebox, located on the far left of the unit.  I've used the Feldon calculator to determine the size of the firebox in relation to the chamber volume, air intake, heat exchange, and chimney size in sq inches(chimney not to scale).

C. Cold smoker (same method as B, less fuel) - any suggestions for modifications that can aid the conversion from method B to C? (basically a way to variably restrict heat exchange while allowing smoke through the gate)

D. Wood grill - rebar/metal cage on right will have bracing to allow insertion of firebricks at 32" height to simulate Argentinian-style/Santa Maria style cooking, with a variable height grill (likely with a wheel)

E. Rotisserie - employed in same manner as D, suspended above unit on right

Questions

1. The firebox intake and heat exchange openings are sized according to the Feldon calculator, what I'm wondering is if the fact that the cook chamber is vertical rather than horizontal matters here.  The point is made on the calculator page that a vertical cook chamber will require less of a chimney but it's not made clear to what degree, any ideas?

2. Materials - I've used firebrick for the firebox and floors of the wood grill, smoking chamber, and coal dump.  I'll also likely line the insides of the wood grill area with firebrick.  Any other suggestions of where I need to use firebrick rather than regular brick and any advice on whether a special (expensive) heat-resistant mortar is needed or I can just use standard-grade mortar?

3. Any obvious issues/design flaws?

Key to images:

Unit is completely enclosed on left with steel lid on top to access grill and door on bottom to feed coals, remove ash

Unit is open on front on right side (enclosed on 3 sides) to allow gathering of coals, access to wood grill

Grid Scale 1:1"

Dark Yellow - Firebrick

Light Yellow - Air Intake/Heat Exchange Openings

Dark Red - Regular Brick

Grey - Rebar/Metal

Dark Blue - Ash/Coal Door

Dotted Black - Grills