1400 sq ft seems a little small for a roof. Is that the floor area or the size of the roof (taking into account of the pitch). I did mine for about 14k (inter-terrace) with the similar materials you are taking about (TBF Romane), including wooden battens, bubble insulation, gutters and colorbond flashing. No leaks so far even with the heavy rain. Though I must say my neighbor German pantiles tiles looks nicer though.
Changing of the wooden structure will cost significantly more, but I got multiple quotes from many roofers, it seems that there are some who will insist of changing the wooden structure at a very high price (30k). Which is not necessary for my case. Maybe you should ask them to quote and replace only the rafters that are damaged. Normally they charge 150 to 300 per piece.