Oh, a Dragonite solo run sounds pretty easy, I mean you would be okay up 'till Ecruteak City and by then you can get some tms from somewhere to help and once you get to Dragonite well it'd be easy excluding the ice type pokemon.
The Tyranitar one I'm not so sure, I've only gone with Larvitar and a bit with Pupitar but didn't like it so I went back for a Larvitar which did fairly(sp?) well.
Meganium, well it's pretty good when you have a whole team but solo'ing it sounds pretty hard.
Pidgeot well sounds pretty good depending on its moveset.
Ariados.....well I've never used one before but if you like them I'd go for it. Does Ariados learn Psychic by level up or something 'cause the tm only comes out in Kanto, I think.
Scizor, well I sorta thought of doing one too starting as a Scyther but didn't know how to evolve it without being able to trade so I left it alone. Starting as a Scizor sounds pretty easy like you'd barely take damage in the first gym unless they spam mud-slap. You also wouldn't get the Wing attack
.
I vote for you to go with Ariados!