I am the Kat that Walks By Itself

Hi! I'm curious how you found me, since we don't seem to have any friends or comms in common.

The apocryphal webcast, "Scream of the Shalka", showed the Master as a prisoner inside the TARDIS, an arrangement the tenth Doctor would have been willing to facilitate.

Yes, I really liked "Scream of the Shalka".

The problem with redeeming the Master is that the character has never been particularly well defined; he's a killer with no motive, a malicious force with no real purpose beyond menacing the hero and being trounced every single time (which makes it hard to see him as an actual threat). So it's hard to imagine an actual persona beyond or without the villainy.

I'd disagree that he isn't well-defined; yes, the earlier Master (especially Ainley) seemed like an aimless megalomaniac, but I think there's always been a touch of rivalry with the Doctor, a desire to beat him, which was shown more explicitly with the Simm!Master.
And the advantage of a fuzzily defined character for fanfic, is that the fanfic writer can extrapolate and fill in the gaps.