Widget development: giving each post in the loop a different format

I’m creating a “latest news” widget, and I want to let my users choose how they are going to be displayed, from a list of fixed choices.

The thing is, for whatever option they choose, I need to display each post in the loop with a different format.

For example:
– layout 1 displays a single row with a single article;
– layout 2 displays a single row with three different cells, one article in each cell;
– layout 3 displays 2 rows – one with a single article, and one with three articles;
– layout 4 displays 2 rows, 3 articles in each.

And so on.

Any idea how I can accomplish that?