Hi,
you might find this webpage useful.
http://vk1od.net/transmissionline/VSWR/VSWRMyths.htmIt seems that if you have a lossy line, the actual line "power loss" increases with the VSWR. However, according to the webpage, it may not be that much in practice. Note that "power loss" degrades the maximum achievable SNR. For a transmitter, it also reduces the maximum achievable efficiency.
Another thing to mention is that for very wide-band systems, a VSWR can actually distort the signal since different frequencies will see a different impedance.
Lastly, the conclusion of your analysis is kind of wrong. If the input impedance of the FET is treated as purely capacitive, then it is never possible to power match to the FET. Conventional matching schemes (inductive degeneration for example) deliberately add resistance to the FET input impedance in order to provide an impedance to match to. If we treat this resistance as infinite, then an ideal match to this infinite resistance will produce an infinite voltage at the FET input, and therefore, the matched design gets a larger signal voltage than the unmatched design.
regards,
Aaron