Are we simply trying to copy the US again? It's not really possible with our system to have 'leaders' debates, as we are not electing a President. There has to be all-party TV debate, surely, and this will never be possible given the plethora of groups demanding to be involved.
This could end up like being Question Time without the audience chosing the questions. I also think the broadcasters have got themselves in rather dark waters with their refusal to include a representative of the Scottish Government.
The argument that they are not a National Party, as in UK party, is asking for futher trouble as all the SNP would need to do is put a token candidate up in one of the English border regions where thousands of Scots live and then claim that they are a National Party.