We've had a Citigo with the 75PS motor for over 3 years and I love it. Great fun to drive and the engine just screams 'SPANK ME!'. So I do. It still returns well over 50mpg. I asked for a test drive of the TSi of our local VW dealer when it was announced, but gave up after about 3 months of trying. Talk about apathetic.
I'm pretty sure that the engine you've got there is the perfect match for the A2; very light, free revving, willing and frugal, all topped off with an infectious three-pot thrum and a gearbox with a very light action (makes my A2 feel like a truck). Suitable candidates from scrapped A1's on ebay can now be had for not too much money. I recognise quite a bit of A2 DNA in the running gear of our Citigo on the rare occasion I've had cause to get under it.