Hi,
I try my best to answer your below queries,
Latio has a larger interior than Vios, after putting two child seat, there is still room for one at the back.
1. Autoaid does it approx. $400-$500. Check the forum, there is on bro here able to do it at a better pricing
2. If you are afraid of CVT issues, get 4AT
3. Damm steering coupling, that goes tok tok..tok. But no safety issues, just irritating
4. Nope, still enjoy driving my 6yo Latio.
5. Sorry not interested, ah pek already. Cannot take speed