You wont find Ann B here- this is where you post a design dilemma

I'd say there's not a lot you can do with the garage, overall height limits and ceiling height to garage perhaps? Limited info and unfamiliar with site, etc. so just really guessing here. The stairs however could be changed as could the balcony, etc. Can't see issues here why it can't be amended to suit your requirements. You never mentioned the issues with the designer but perhaps stay with them as redesigning through another may not be ideal either! Some won't touch another designer's work and will start from scratch. Give them another chance to explain why it is all done this way. Allow them the opportunity to amend it and depending on your council, use a SECTION 96 if possible. Council will soon let you know if they can accept it. Remember they've been submitted so I'd have to presume you were happy with them beforehand. Clients changing their mind or have difficulty making decisions happens regularly as its all quite new to them. I too have had clients that love the plan's, get submitted then decide that want to change something that has been there from the beginning.... Windows and doors are usually what my clients change. Frustrating for client and equally if not more so for the designer as it affects the whole plan set and documentation in many cases. I do know many designers will railroad their clients into decisions based on their own visions but this is never a good thing. It's a collaboration between client, designer, council, engineer, builder, etc. and sometimes a bit of compromise by all parties.

Get a cabinet maker to custom build a work station across the entire width of that blank wall. As it is on full show I would recommend incorporating mainly cupboards and drawers so you can hide stuff away. Consider using a coloured polyurethane and nice stone bench top and cabinetry hardware, as it will be the first thing guests see when entering your home. Contact me if you would like further design suggestions.

imo the biggest challenge/cost would be removing all those big solid walls, changing doors and windows and repairing ceilings and not the extra plumbing (new bathrooms and kitchen cabinets, fixtures and appliances cost the same regardless of the extra few metres of pipes) and a new location can make the most of the available space but it can sometimes be more cost effective to add an extension rather than attempting to squeeze too much into an existing building but you need an engineer, builder and plumber to give expert advice on site ... better not to assume that one option is better than another but collect a variety of ideas and ask for quotes to compare actual prices but do you have a realistic budget? i would expect to pay at least $50,000 for a modest new kitchen and bathroom in the same locations before removing any walls or adding an extra bathroom and new laundry and the combined ens/wiw is too small and would be better to have a good sized ensuite with biw and there's not enough space for a bigger island without compromising space in the family dining area...there are so many different options but we need more info...are there any good or bad views, what is the length and width of the block, is there a garage, is there car access into the back yard, what is the distance from the house to each boundary, describe your climate, where is north on the plans, how many steps are there from the back and front doors to the ground, does the block slope and in which direction, how much headroom is under the house and in the roof space...is there any potential for an upstairs, downstairs or an extension into the backyard?