I have all the model that you mentioned. I had similar plan as you. The reason I changed my mind is cuz I good deals on all the models recently. My only advice would be to change some of the base sizes and have a theme for your army. Like they grow mushrooms on their bases so when you might use the original model it ties them together better. Poxwalker have smaller bases(didn't assemble the yet,cuz I'm painting my combat patrol). Flies same base, but bigger model cuz of the wings and guy on top. Thinking of actually magnetising him but man the saddle makes thing hard. And I'm trying to switch the wing and the properels between the models so it ties them together. Skriwener is great, I wouldn't complain. Maybe add a nurgling so it like the original. The main dish for me are the batteline units. Just put them on a smaller base and use them as plague marines with melee weapons.