If you have a mid range chainsaw and bought an Alaskan small log mill (£139) and the appropriate ripping chain for your saw (£25?) you could turn small to medium logs of up to 15" into planks or beams. You just screw something straight like a bit of 4x2 on to the top of a log to get a straight reference line, then run the saw and mill along the top. Its a kind of 'accurate mechanised splitting', to paraphrase.
I had no trouble milling 15" Chestnut with a 50cc Stihl.
http://www.alaskanmill.co.uk/Store.aspx#P13Its a cheaper version of a Logosol Bill Mill, shown in this video where a pal of mine is doing it on some oak.
https://www.youtube.com/watch?v=SzluOS2nZno&index=4&list=UU7RUv18S4bB5K1WUmXzxmdA...Just a thought.... maybe ?