If you qualify for a mortgage in your name only based only on your income, and your fiancee agrees, you can buy the house in your name. Then you sell, and buy again. This time you have to qualify for any mortgage in your fiancees sole name ( because if it is in joint names you are no longer a ftb and will therefore disqualify both of you) and the house has to be in your fiancees sole name. Three problems to over come then, firstly whether you will qualify for the mortgages in sole names, secondly Sarah W ( who knows what she is talking about) says banks now require house purchases for married couples ( where not an investment) to be in joint names ( although as I have said this is not a legal requirement), and thirdly whether in fact legally it is adviseable to do so.
Also there are exemptions for owner occupiers and reduced rates for them too and who knows what the future holds as the stamp duty situation could change at any time.