So, tell me what you think of conlangs.
Garich i dhôl goll o Orch.
It's kinda fun, personally. I like to play around with language and the grammar of a language.
Did you read the Diamond Age?
In it, mankind has developed a system akin to what you describe, called Logoglyphics. Alas, many uneducated people never learn to read because they can rely on the symbols to navigate life, and as a result the populace becomes inarticulate and petty.
Auxlangs are very silly things that will never see any meaningful success.
Conlangs as part of a greater creative work are kinda neat I guess, though it always disturbs me to think that many of such writers care more about making a world than a story, which isn't working with the medium. You aren't trying to write a series of fantasy novels, you're trying to write an atlas.
No, but I was playing around with Blisssymbolics (http://www.blissymbolics.org/) and it seems as though something like that could actually work -- if you could have a standard system for combining compound words. Basicly something like how a Hanzi symbol is built from radicals and simpler Hanzi. If something like that could be made to work, and a standard international alphabet were adopted for names and places, it could be used anywhere.
What is a "conlang", a thieves' cant? I think you mean planned languages.