I do bathrooms every day of the week and I can tell you now that, If you really want a bath in that space and shower just do a shower over bath I noticed your shower was 800mm wide this is to small for a shower 900mm minimum. Forget the bifold doors put in a cavity slider or if this is not possible do a face of wall sliding door on the out side of the bathroom. If you really really want separate bath & shower move the toilet into the laundry. Get an 1800mm deep soaker bath and run it along the 2000mm wall run your shower along the 2100mm wall opposite the vanity. I take it your on a timber floor not a slab as moving a toilet on a slab can get costly.

Bath v shower. If you go for the shower and no bath, make the space big enough to retrofit a bath in later. Bath is normally less than 900 which is preferred shower width however, If u plan on being there 10 years then can’t loose either way. Talk to your plumber about the most cost effective layout options, for example they may suggest rehanging door to swing other way or moving door to open up other layouts, I agree about corner cabinets, my sister just replaced hers with straight and there is more space not less and much more modern look.

We too live in a cold winter climate with our bathrooms all on the southern side and faced similar issues as you do. One smaller bathroom does not have a window so we put in a Velux skylight which provides amazing natural light through the day. This may not be to your liking, especially if you have a period home. We also use heated towel rails and under tile heating (just enough to take the chill off and stop mould) in winter. Although we have a light in the shower recess, a bonus is the large fixed shower head with inbuilt LED, which at night gives the feeling of showering under moonlight. We chose light colours and mirrored recessed cabinets to reflect as much natural light as possible.

Yeedalong, if you are planning to do the twin japanese style bathrooms, my idea for a second toilet to save on mess and money was to use the following system, they are more expensive but should be more cost effective. I have used this system when staying in a newly restored hotel which was very impressive. You are an artist do you have likewise guests come for workshops etc. https://www.qualitybath.com/discover/post/2758/how-do-saniflo-up-flush-toilets-work?cf_chl_jschl_tk=829adadc38e7871ef5ea3f40d2263ce9590b9723-1584241557-0-AaflrfqRF0EsynbeG7BfUpQTLpTsP9979z3m5I1o9PJtGGD7llERhHsLF7IO5GHUT46QHGo8eWMB9dLlnHpVeu1xGiyqgmC3GLQQfnY7FhGg4Ihwi8L0eRsmGrxROuLzQKC6xuQEYEhVS7u-pxfnEbuq49ceG7NzpVig6I_H5wE3qQuoAzGcro-u7lYyu1OPih1IX2yOhlY4s57LNRhYNL8iH7bJVLdp31Q2WIgQ_STomCtxGtdK_llfflOdfauYpnzNGaH2xpJNt8gb0yOphB_VrJJS6mjIkN5hJIH2B2OVEUTrasCFiJU6wfcNa5R545BqYMbzsRlVt706x4H4VdQGu7vITBMsxxuCkxwjoHFqkR_VKKXXY5jrE_n5Bo4hj29DQn0N-9XUjJ9htfOpfSg