I don't know Lattice so I would not use it.
I'm not even mentioning trust issues, when sensitive data is involved.
Doing anything less and hoping that companies would use your toy project is just wishful thinking. Sorry to be that guy, but please get real.
Browsers are complex because they solve a complex problem: running arbitrary applications in a secure manner across a wide range of platforms. So any "simple" browser you can come up with just won't work in the real world (yes, that means being compatible with websites that normal people use).