Power Supply for Servo System (Hot Supply using Variac)

I want to run my servos using 130VDC MAX and my plan was to build the
supply using toriodal transformers, bridge and big cap. This will
work but a friend of my came up with something today that I can't
think of a reason not to do but seems too simple to jump into.

Remove the transformer and put the input to the bridge right to
120VAC line. First this would give too high of a voltage(approx
168VDC) so then he said use a variac(adjust 120VAC from 0 to
140VAC). I do have four 10Amp Variacs available but was wondering if
there is any thing I am overlooking in doing the supply this way.

The only thing I thought of was no isolation but what is that buying
me?

Should I buy the toroidal transformer or will this work just as well?

Any comments would be greatly appreciated.

Thanks,

John