As far as technical challenges, these will be enlarging my negatives to that size, I have worked up to 20x16 but not consistently. Also calibrating my workflow with a friend of mine who has a completely different set up to me, his vacuum frame is around 8ft x 6 ft and he uses an 3k HID lamp. These should be overcome with practice and a good few step wedges. Obviously handling such large sheets of sensitised paper and developing will be a challenge, aswell as drying.
Practice will be key and a lot of patience, I expect there to be quite a high failure rate initially, however I think this is part of the course. Silverprint can supply dev trays upto 4 ft, I have found a much cheaper supplier for Cyanotype II which helps, as I will need about ½ litre to begin with.
In relation to aesthetic challenges can you give examples of what you are you referring to, as I am bit confused as to what you mean. The final print might exhibit more grain, however for prints of 30x24 the viewing distance will be quite different to my smaller work so I am hoping this will not be a problem.