I would probably ask for a design from an A/V Integrator with understanding that they will not get the follow-on build contrast. This can happen from a A/V design consultant.
This ensures that when you submit for bids, that all the integrators are quoting to the same design specification. It flattens the playing field and gives you a clear idea of cost.
The consultant should NOT include wording which requires the integrator to take responsibility for a 'full and complete' final design. That's the consultants job, and you should hold the consultant to that requirement as many consultants half-a$$ their work and copy and paste quite often instead of giving customers the actual engineering that they deserve.
If you don't want to go that route, I would talk to Stewart Filmscreen.
If the area of projection is outdoors exposed, then you need to use a PVC or glass screen, I expect, which is weatherproof and can sustain the building code requirements. Projection is always a 'film', but it can be built into glass materials or applied after the fact. It should live on the inside of the surface rather than the outside to help protect the material.
There are advantages to going to a mirror bounce vs. a direction projection option.
With a 9m wide screen, you will typically be dealing with 5.6m of projection height with a 1920x1200 projector. There is no changing the height the projector hits unless you use a specialized lens, or a mirror designed to compress the image height to what you need (both are possible).
So, something like the Panasonic PT-RZ970BU can do it, but even with their UST lens, you don't have enough room.
About .4-.9 is short throw, .3 or lower is really a UST lens, and with 1.4m to a 9m wide screen, you are very much in the UST category. Even with a .3 lens and a mirror, you don't have much room.
So, yes, two projectors seems to be the absolute minimum requirement.
I would recommend something like the Panasonic PT-RZ670 model which is 1920x1200 or the RW630, which is 1280x800. Depending on viewing distance, resolution may not matter.
Pair it with their UST lens, the ET-DLE030 and you will have a good 20,000 hour solution to what you are asking for.https://panasonic.net/cns/projector/products/rz670/specifications.html
The projector runs around $8,000 per unit, but the lens is an additional $5,000 per unit.
This setup should deliver about 43 lumens per square foot of screen space with a 9m wide image and two projectors side by side.
There are models in the same series with a bit more light output if you want to add 10% or more brightness to the setup.
Really, it depends on how bright things will be when in use, but rear projection really helps to combat ambient light in the space and preserve black levels.
You should talk more about what content you intend to show, where you are located, and what levels of brightness are being dealt with.
The drawing did help.http://www.projectorcentral.com/Panasonic-PT-RZ670BU-projection-calculator-pro.htm
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