For the best high-resolution result, you generally need to get the camera closer to the fresco’s height rather than relying on heavy perspective correction afterward. Software can fix some keystoning, but strong correction throws away image area/resolution and is not ideal if fidelity is important.

Possible solutions mentioned:

• Tall camera masts / sports camera masts / aerial masts can raise a camera several meters indoors. They may be rentable, but they can be unstable at full height and often need stabilization such as guy lines or weight bags. Remote camera control and precise aiming can also be challenging.
• Very tall tripods exist, but have similar stability and control issues.
• A shift lens is the usual architectural solution for perspective control, but at this height and distance it may not provide enough adjustment.
• If image quality and accurate framing matter most, a lift is the strongest option. A mast lift may be more compact than a scissor lift and easier to use in tight church interiors.

So: if this is an important, high-resolution reproduction, a lift is likely the best answer; otherwise, a tall mast support is the main lower-cost alternative.