The point of having a top-of-page button is for ease of use, so
that the person using a mouse doesn't have to switch to the
keyboard.
IMHO it is far easier to bang on the home button than it is to find (and
recognise in the first place) some random link and then manoeuvre to it with
the mouse, given that I don't even have to actually look at the keyboard to
find the home key.
Are you going to provide an on-screen keyboard emulator so your person can
use that to enter their login credentials?
And how do you scroll down to start with? With the easy to use PgDn or [down
arrow] keys or that pesky hard to use scroll bar (assuming you don't know
how to use your mouse wheel)?
Which brings up another matter, the scroll bar. If you *insist* on using the
mouse then simply use it to lean on the blank bit above the scroller (not
the arrow, the blank bit). In pretty short order you'll be at the top of the
page, so browsers *do* have a built in to-the-top-of-the-page "button". To
hurrry up matters hold down the Shift key while clicking on the top of the
scroll bar. Oh, I forgot, no keyboard usage allowed