The layout of the kitchen is functional as is. If you move the oven to the other side it'll be too far from the sink for hot liquids, plus it'll be in a walkway. In it's current location the oven would be next to the doorway (but not a thoroughfare) so be sure to leave 200mm beside the oven. A pull out spice/oil rack would be ideal. By leaving the oven in it's current location you'll save on electrical costs. The fridge would be ideally located where your proposed oven site is. A broom cupboard could be placed next to it to make up the space. To let light in I suggest cutting out a small section of the tin roofing in the pergola area and putting tinted polycarbonate roof sheeting in it's place. IKEA has great kitchens flat packs that are easy to put together.

my suggestions include swopping the smaller wiw for more bedroom and bathroom space rather than an extra bathroom and the entry to the master bedroom has been moved to allow a little more space for the ens and wiw and downstairs i suggest combining the living and dining area and using some of the under stairs space for bedroom storage for the guest room...having the patio on the north side would allow inclusion of the extra outdoor space up to the laundry door into a more spacious outdoor area with the barbq along the fence...your concern about using the pation in winter would depend on the climate but the northern corner of the house will be the best aspect during cool weather but the patio an dany other windows may need sunshade from the western sun

I'm in NZ , and we have things called Gottages -- basically , a square double garage , but with a large glass door instead of a tilt door -- a cottage that looks like a garage . If you provide the concrete pad with sewerage and power and water , they seem to be around $15-20k erected . You then add insulation and linings , and then internal walls , shower , kitchen , etc . So lets say the pad and prep is $10k , the gottage $20k , the interior $20k , $5k for a basic kitchen -- you'd have your 2 bedroom for say $55,000 . Likewise , tiny homes on wheels seem to start around that , but $80-100k would be a high standard one with solar panels etc , and the advantage is they can be resold , the disadvantage they are maybe half the size of a gottage . Both the above are designed to be relatively easy to get council approval , of course you could try to build something yourself using demolition materials and old packing crates and mixing muesli with the dirt and stampoing on it to make the floor , but I suspect the building hitlers would make life not so much fun . It would be tight , it wouldn't have much flair , but I'd say it could be done for $120k .

Sketch the room with measurements and post here. Pics are good also. You’ll get some great ideas.