Bas-relief for hallway wall: on-site modelling, foliage, paint

I have a blank wall in my entrance hall, roughly two metres wide and two and a half metres high. There is nothing on it at all: no window, no sockets, no furniture, just an empty plane that your eye runs into the moment the front door opens. I would like a bas-relief there. The subject is plant life: branches with leaves that start almost flush with the plaster, gain volume towards the middle of the composition and then sink back into the flat surface at the edges. The relief has to stay low, three to four centimetres at the highest point and no more. The hall is narrow, people walk past that wall every day in coats and with bags, and nothing should catch a shoulder. I also want the composition to turn the corner instead of stopping at the edge, so two or three branches should continue onto the adjoining wall. Otherwise it will read as a picture in a frame rather than as part of the room.

Before any modelling begins I want a scale sketch tied to the real measurements of the wall, and after that a trial fragment modelled in place: one leaf and a piece of branch. I want to look at it in my own light, in the evening and in the morning, and approve the plasticity before the whole plane is covered. Please check the substrate honestly and tell me what you find. The plaster is old and sounds hollow in a couple of places, and I understand that a relief modelled onto a crumbling layer will simply come off together with that layer. If part of the wall turns out to be plasterboard it has to be reinforced, because thick relief has real weight and a sheet without a frame behind it will not hold it. Mesh, primer, reinforcement, cutting back the loose plaster: put all of it into the estimate openly, I am ready for that part of the cost.

I know the work is wet and dusty, that the modelling will take days to dry and that drying must not be forced with a hot air gun. I would rather wait an extra week than live with cracks. I expect the floor, the door, the light fittings and the furniture to be covered, the waste to be carried out, and the flat left clean at the end of each stage. The flat is mine, so I can make an irreversible decision; in a rented one this kind of decor cannot be removed without replastering the wall, and that would have to be agreed with the owner in advance. For the finish I want paint in the tone of the wall with light shading or a glaze, so the leaves read by their own shadow rather than by colour, plus a discreet side light grazing the surface so the volume is visible in the evening. The subject should be your own drawing or based on free sources; I do not want anyone else's composition copied.

Please include in your reply:
— how long the whole job takes and how much of that is drying time;
— the price broken down: substrate preparation, modelling, painting, lighting;
— what material you model with and how you deal with weight and reinforcement;
— how approval works: scale sketch, trial fragment on the wall, rounds of changes;
— examples of similar work of your own authorship;
— how you handle covering, dust and removal of waste.