6m x 18m shed conversion in Adelaide hills (sample sketch)

G'day, I have been looking in to converting my shed into a project studio for a while now and am just about ready to put my plans into action. I live in South Australia on a 55 acre property in the Adelaide hills. My closest neighbours are about 500 metres away, and between us and them is a few thousand cherry trees as well as some bush. To save on expenses, I hope to use materials that are lying about the property, this includes a moderate stockpile of timber and steel, as well as general building materials (bolts, nails, hardyplank etc). I have access to all the tools I will need in order to do the job with the exception of a large concrete truck and pump). If possible I hope to spend less then $20k (aus) but am not fussed as to how long it will take. I would however like to get it started before this november. The Shed itself is approx 6m x 18m supported by 7 large steel frames spaced 3 metres appart. The roof at its peak is about 5 metres high and at the level about 4m. No slab has been layed so I am unsure of what to do about the floor (maybe stumps?) The whole structure is covered in corrugated iron (and at the moment surrounded by blackberry bushes that reach the roofline but I'm taking care of that) Running parallel with the shed is another 70sq metre shed which I would like to keep as a general purpose shed. Beyond all this I am have at least a dozen willing helpers to carry out the labour (these include 2 sparkys and a chippy and two painters (me being one too). I have included my rough sketch-up to give you an idea of what I'm thinking:) BTW: this is my first attempt at using this tool so forgive the sloppyness. Some of my ideas include: Mud brick or adobe feature walls Round cut tree stump floors Cathedral cielings in control room (dunno if this is any good) Laying slab for control room only to isolate it from lo freqs And maybe skylights. I am still planning so by no means is any of this set in stone, so if anyone has any ideas or suggestions I would be very happy to hear them:) Cheers! Zed