I am going down a similar route. I am lucky enough to look forward to a new shed in a few months time (after the fruit trees have done their thing as the build will be very close). I have planned for the extraction system and compressor to be housed in a 'lean to' section with the 4" ducting and airline entering via the end wall. At present I have an old version of a Axminster SFCA-200 with an home built 'inline' collector for larger chips etc. However I will be fitting a roof mounted filtration system (probably from Axminster) as well.