Cophasing two (or more) antennas can be made to work on a mobile. There are problems associated with it, doesn't really matter what antennas you want to use. Probably the biggest problem is distance between antennas. Something like 1/4 wave length is the 'minimum' that's usable for a half-way directional radiation pattern. That directional radiation pattern is the only really good reason for cophasing antennas. That directional thingy isn't just limited to one (bidirectional) direction, you can switch it 90 degrees without too much trouble. And since that directional thingy is pretty 'broad', never gonna be razor 'sharp', you can cover all directions pretty well. It can get complicated, but it's certainly 'do-able'.
There's no accounting for taste in 'looks', yours, mine, whatshisname's. 'Looks' doesn't do anything for performance.
Running high power. That's a completely different thing all together. Get the antenna system working, then worry about power. One problem at a time, otherwise you'll drive your self nuts.
There is no 'sure thing' when doing cophasing. Unless you can get me to do it for you! Bring lots of money! (I can be bribed with beer.)
- 'Doc
...that's not gonna work, is it...