I'm no expert I just know a lot of people are doing cement board around me. I am not sure if they glue then screw and caulk to prevent hiding spaces. Best to check with an expert. However. It can all have the same look with a smooth stucco or other surface and scoring. Here is one with a slight two tone chimney. Not to much but enough to diminish the height a bit .

I love your Mondrian inspiration. First, figure out which software you have access to that you can use to experiment with exterior ideas. If you can use Photoshop, you are ahead of the game. I can’t justify the investment, so I limp along with Microsoft PowerPoint and the free Sherwin-Williams ColorSnap. Even if you do 20 or more experiments with color and color placement on the photographic images, it doesn’t cost much money and doesn’t take much time. Keep going until you come up with the right combination. Since the house has shingle siding, I am assuming that you cannot just paint it to get the Mondrian look. Are you going to change out the windows to get the heavy black frames? Are you going to reside the whole house, or just the front? To get the look of rectangular panels, you will need to find out what products are commonly available in your area. For instance, James Hardie panels are in common use. Example: Drive around to construction sites. Find out what products they are using. Get the names of the contractors. You are going to need to hire someone knowledgeable for the installation.

I have a house that's very MCM on the inside and rather ordinary looking outside. we updated our garage door and it made a huge difference. (it's like the one pictured below, but in white.) I really like the mockups celerygirl posted. I think her ideas are going to be your best bet. you're not going to really be able to make your home look like a true midcentury, but improvements such those will make it look up to date and MCM inspired. I think funky landscaping can really help, and don't forget little touches like lighting.

Your wooden gate is a more rustic style, so you might want to modify it - trim off the dog ears and change the hinges. Agree about the porch post - the style is all wrong for the house. Boxing it in is pretty easy. Also agree about landscaping If you have paint or photoshop, play around with different colors for your trim and siding. The current colors are neutral and safe, but there's no pizazz. Looks at blues, grays and greens, which will work with your brick and roof. I'd paint the window trim too, and look into beefing up the trim with some additional, but simple, molding. I can't see the detail of your front door - if it is a rustic, colonial, victorian etc style, plan on replacing it eventually - and yes, a lighter or brighter color. I don't see how you could remove or replace the "beam" (if I am looking at the thing you mean - across the front, above the windows?) and come up with anything that is better. Your brick ends below it; it is appropriately simple; although it is too bad that it sits right on top of the windows. Perhaps you could paint it to blend in with the brick, but I think just painting it with the rest of the trim is fine.