It sounds like your home had floor furnaces at one point. The large return air grilles sound like old openings for floor furnaces, used a long time ago. Where to start? First, your system should have filters somewhere in the return duct or inside the air handler or furnace. I would look really good to make sure you haven't missed something. I've seen filters placed in really weird places. Sometimes filters aren't found for years. By then they're pretty stopped up. As far as the return grilles being large, the larger the better! One thing that kills your system and your energy efficiency is duct work that's just too small. Modern systems are made to run with very little static pressure in the ducts, around 1/2 inch. That's not much, so I wouldn't worry about the large ducts. The filters are another story. You really need a filter in your return duct somewhere. If there's not one, i would install filtration. Usually the cheapy filters work best as they cause the smallest pressure drop in the duct. You mentioned the refrigerant leaking out. If you have a refrigerant leak it should be repaired. That stuff ain't cheap. Besides it's illegal for a technician to keep adding without repairing the leak. If someone is having to add refrigerant, you definitely have a leak, no question about it. If the service provider you called did not look at your duct work, did not tell you your system had a leak, and did not offer sound recommendations, please ditch them and find someone qualified. As far as your system coming on and off every ten minutes or so, that's called "short cycling" and isn't good for your system, your energy costs, or your comfort. It sounds almost like your system is either too large for your home or you have massive air infiltration. Either way, this needs to be addressed. Really, I would recommend you find a good service provider in your area that can be trusted to offer technically correct advice. I usually find it best to ask friends, co-workers, or other family who they use and trust. In the meantime, you may want to check out a couple of articles I've written dealing with heat loads and your comfort. Here's one HERE if you would like to read it. Let me know if there are specific things I can help with. I'll be happy to help if possible.

"The moving of the sink on the right-hand picture, is this to allow more food prep space?" Yes, and to allow you to prep in front of the window. Any way you lay out the kitchen, you're going to have a traffic path through the middle, except for a U, which takes most of the dining area. You need to think about how you enter, how guests enter, and how you want to use the kitchen. Here's another plan with a nice prep space, with the appliances arranged more like cpartist suggested, but it keeps the peninsula across the room, and preserves the dining area. You'd have your back to the long hall and front entry--that's probably really bad Feng Shui, but if you'd prefer the sink under the window, then it's a good plan. What size fridge and sink are you planning to use? If you have 118" available on the top wall, and subtract 24" for the cabinet on the right, 30" for a sink, 30" for the fridge, 24" + 2" for the DW and return panel, plus a couple of inches of filler beside the sink cab, that leaves 6" for the pull-out/filler beside the fridge. If the fridge will be enclosed, subtract another 2-3". I don't know if that would be enough to allow the fridge door to open far enough to remove the crisper for cleaning.

I came to this forum from kitchens where I spent a large partt of my life for a while. My kitchen planning got stopped cold by an injury and then restarted with some different ideas. I tested them and reworked and retested until I was pretty comfortable I had the best possible for my situation and limitations. I held my breath and posted my plan. I asked for thoughts on one specific part but got a lot of challenges in general. I could get upset or defensive, but I realized I had an answer for why each of those things was in the plan as it was and I didn't want to change it. I got reassurance on my one question, and then I knew I was ready to move forward. You have to test your ideas. That is the least expensive and most important part of the process whether you are building or remodeling. Changes only get more expensive and when you cant change, regrets may be forever. Those hard feelings are likely to be much greater than any you may get over a "this is the biggest investment we will ever make and where we plan to live forever - we get once chance to make it great, so I'm sure you can appreciate that we want a double check from someone who hasn't been too close to this." Consider that the family member may feel the same away about giving you feedback, criticism or questioning the things you say you want. Guarding each other's feelings is the best recipe for unhappiness for both of you. Ask any first year law student about the number of family matters in their case books. If you can't question a family member or get a second opinion now, it will only get worse once you start. If your family member is worth their salt, they will understand and will want you to get the best possible result. Ask the second architect to do a reality check for how this will live and spot problems, not do a redesign. Just make it a team approach moving toward a common goal, not adversarial. If you can't do that now, I'd scrap the project. Seriously -- this is a huge investment of time, money and self. Can you really afford, financially, emotionally and in terms of family relationships to not be happy when it is all done? Now is the time to test nerves, bang heads and check and recheck plans -- not once the work has started.

second decorenthusiaste and queenvictorian until we see photos and plan it's hard to advise properly my general comment though would be-is there any need that you can meet in that master bedroom, besides sleeping and other bedroom-y stuff, and working in the office? just an example-say I'd have this space..I'd think..great, I can fit a library in here (because I never have enough space for books, and I find them very calming too) and you might want not a library but something else what is something that you can do there, would happily do there, in addition to other things? first, define your needs..in this case wants and desires, since the room is so large. After you think: ok I'd rather it function in a way such and such"-you think of a plan-what has to be there, what'd be cool to have there, how to get from that plan to reality.