As a contractor I can tell you that most reputable contractors probably don't need your job, and if you make things too complicated or troublesome, they will move on to other jobs that don't throw up red flags. Much of what you ask for here is reasonable, but bringing a second contract into the equation can set of some alarms that you may be a difficult customer to work with or even a litigiously minded person who is likely to try and bring a lawsuit whether deserved or not. Anything you want covered should be in the original contract.
It's totally legitimate for a professional to charge you for a design, at least in some situations. If the contractor has a book of ready-made designs and just pulled one out to show you, then you're right that s/he shouldn't charge you. But if someone does a design that conforms to your room's dimensions, with the features that you want, then that person has invested time in creating a work product. Some contractors and architects think that's just the cost of doing business, but many others consider that their time is worth something, and they charge for it. You just need to let contractors know that you're not looking for that kind of custom work, and not willing to pay for it.

I have a new home plastic/fiberglass shower stall with a glass door and side panel. Two side are the plastic and it is probably 8' tall. I do not want to enlarge it at all. I want to just replace. It is like an inset that was there when we built the house. Not fancy. It is a white/cream color and I would just like something nicer to replace it. Anyone intrested in the Spring, Texas area.
20% labor price ---out of the question----I'm a Building Contractor, If you are totally remodeling a bathroom, where is the cost for demo of existing???? Demo can easily run an extra 10%- factors: 1) Age of existing---many factors here to adjust price, 2) Accessibility ---Getting materials out of and to the bathroom, and protecting present surroundings of owner. 3) Cost to dispose of debris 4) Where is the Contractor's O & P ???
Both Lowe’s and Home Depot offer bathroom remodeling services. Home Depot remodels cost $5,000 for a powder room up to $30,000 for a master bathroom remodel. Lowe’s suggests that customers expect to pay at least $100 per square foot on bathroom remodels. Both stores offer repairs on your existing fixtures and installing upgrades or new replacement parts.
My suggestion is when talking to contractor be subtle and ask your questions. Ask if he/she will have a dumpster or trailer to haul away debris. If the don't get dumpster or have a trailer then you probably don't want them to work on your home. Tell them your concern with the only toilet in the house. Unless it is not safe I have always reinstalled the toilet so it could be used at night. A good contractor will work with you in anyway possible because you are the key to more business.
There are so many beautiful things to notice about this bathroom that it's hard to know where to start. The concrete sink? The wallpaper? The sconce lighting? The tarnished mirror on the door, reflected in the main mirror? The barely-there ultra-modern faucets? Whatever you notice first, though, you can't but admit that this space is a masterpiece.