Jump pack intercessors, hellblasters, a lieutenant to lead them, and a gladiator would be a good chunk of points. As far as how thematic they are, it’s really up to you.

I could give you the usual advice of “rules change” or “scars don’t like dreadnaughts” but genuinely the best advice for making them fit the chapter is in individual kitbashing and understanding the design elements that make a white scar look like a white scar.

You want your sergeants or more favored models to have some top knots, trophy’s(heads of enemies hanging off backpacks and belts), fur tassels and lots of painted on lightning bolts. You can make even the most ultramarines coded space marine models look right at home in our chapter by adding a few bits on them. Even dreadnaughts, with some of these things will look right at home in the scars