I agree that the GM produced transaxles might be a good option but I cannot get my hands on them. Its very tempting to buy a motor from ebay which I cant find here, specially the corvette engines, but the shipping costs are really high which add to the already expensive engine.
I got the idea of building a space frame chassis from the ariel design itself. Although the ariel atom has a bit formula-ish look to it, I intended to give my build a road car look.
And as for the updates, I don't start building till mid 2016, got plenty of time to research.
Muneeb