Boiler feedpump energy consumption and safety
There is research that indicates steam driven feed pumps may be more efficient for boilers rated 300 MW and larger. VFD driven BFW pumps seem to have been the preferred alternative for 30 years. Various types of electrical and electromechanical variable-speed drives have been used for more than 90 years.

There is likely a lot of literature about energy consumption and safety. Study the literature and form your own opinion.

A Comparative Study on Economy of Driving Mode for Boiler Feed Pumps
Xianyong Peng; Peihong Wang
Power and Energy Engineering Conference (APPEEC), 2010 Asia-Pacific
Year: 2010

Adjustable-speed drives for thermal power plant boiler feed pumps. Russian and American experience
Oliver, J.A.; Samotyj, M.J.; Shakarian, Y.; Vinitsky, Y.
Electric Machines and Drives Conference Record, 1997. IEEE International
Year: 1997

Power plant auxiliaries and their relation to heat balance
Penniman, A.L.
A.I.E.E., Journal of the
Year: 1924, Volume: 43, Issue: 2

Power measurement and harmonic analysis of large adjustable speed drives
Oliver, J.A.; Banerjee, B.B.
Energy Conversion, IEEE Transactions on
Year: 1988, Volume: 3, Issue: 2

Computer based Boiler Feed Pump protection and changeover scheme
Vinurashini, R.; Jayasri, R.; Veerapriya, N.; Umamaheswari, S.
Energy Efficient Technologies for Sustainability (ICEETS), 2013 International Conference on
Year: 2013