Is this correct?

I am wanting to know that if this:
D:6
A:6
E:4
can replace this
D:6
A:6
D:6

and the frets can be changed as long as the frets are not below 1

I'm asking this because I am looking for solutions for not having to do drop D every tab i see
and I have seen at least 10 tabs that have no open D(top) so is replacable if my little method works

Yeah - that should work as you say as long as you don't need to go lower than a low E. I do it with some tunes, although you do lose a bit of depth of tone...