A chippy can create any kind of decorative effect you desire (its just fibre board and mouldings) and you can vent the mechanical hood under it. I have a godawful stainless steel modern hood in my vintage cottage. I'm sure the last residents loved it, but they failed to actually have the hood vented properly. It just vents into the roofspace. So I now have the opportunity to remove the largely useless anyway hood and start over. I'm planning the same as you. A faux hearth, boxed in with fibre cement board and then with decorative mouldings attached. The actual mechanical part will be properly vented outside.

The choice of oven will affect the layout of your kitchen. You want an efficient layout, which is what I'd describe as the working triangle (fridge, sink and oven/cooktop). The advantage of 2 wall ovens is that you can be cooking 2 things simultaneously (like a roast and desert at the same time - 2 completely different dishes) which makes your time in the kitchen more efficient. There is a trend towards multiple wall ovens for kitchens, so this will add value to the property as kitchens are a major selling point. If you go ahead with an underbench oven I'd recommend it to be 900mm wide and with a matching cooktop and rangehood, because it a family home and anything smaller will not cater to your family or add value to your home. The picture below is an example of a kitchen with multiple wall ovens. For this particular project, there is a butlers pantry where you'll find all the electrical kitchen appliance including the microwave. I would also say butlers pantry's are very desirable at the moment and even necessary like an ensuite. From the floor plan you've provided it looks like your pantry is open, you could consider installing a sliding door to achieve a butlers pantry. The other option for your microwave is to include an open shelf in your island bench. Just make sure you have a power point installed which shouldn't be an issue since you have the dishwasher located there also. Good luck with your project. Looks like you have most of the major design questions resolved.

It is regulation to have 200mm either side of your cooktop, to the nearest panel or flammable surface if it's gas, so that would mean a minimum of 1000mm opening, not odd at all centring your cooktop, although consider overall balance and proportions, consider side bench height cabinets, at 450mm deep X 200mm wide to create a column either side, which the 'mantel' element sits on. That creates a 1500mm mantel, with your rangehood concealed in a 1000mm box easily accomodating your ductwork. Thesahllow depth cabinets sit on your bench there're maintain a continuous bench top profile, running through, makes everything look bigger, and is traditionally suited to this style. Often these cabinets house spices, oils and condiments.

You can get slim range hoods that generally fit into the wall cabinets ours were approx 40cm deep which housed the complete operation, our plumber ran a 6 or so inch flexable ducting into the roof cavity and out under the eaves. Most brands make these. A photo would be helpful. https://www.thegoodguys.com.au/omega-52cm-undermount-rangehood-oru50x?CAWELAID=620013790000422290&CAGPSPN=pla&CAAGID=21711678566&CATCI=pla-376401441757&gclid=CjwKCAjw0qLOBRBUEiwAMG5xMNN63iJr0n0Bnxf31-Gt0t5s0vERt_lOwOYkC6uzovf9TDWwawry9RoCgxQQAvD_BwE&gclsrc=aw.ds&dclid=CLOv9erawdYCFc0slgodE5oLHg Where we didn't have wall cabinets we had tall boxes of stainless look laminate built up to the ceiling which contained the extraction unit, which was approx 30-40cm's and extraction ducting cheers