A comet or asteroid theory would not account for the thing about the axis tilts. The only thing that really accounts for that is a larger star capturing a smaller one.
There are two types of planets. One type have rocky cores (Earth, Mars, Venus, Mercury, Jupiter). The other type have nothing but gas ~ Saturn, Uranus, Neptune.
If you don't care to work with the "gas blew away" theory you have to come up with some other theory, but mathematically there are several dozen ways all the planets can be accounted for in their present orbits.
I'm finding it interesting that so terribly many suns out there have close in gas giants ~ just like an Early Solar System could have had.
One recent theory backed up with some factoids says the cool down of the Solar system hereabouts happened too fast for gas giants to form close to the Sun.
Been running that one through my mind ~suggests our early sun S L O ... W....E...........D >>>> D O W............N right off the bat ~ which suggests that maybe it got a huge slug of Helium from the original nebula.
Someday we'll find out, of course.