bad idea to buy a larger suit and have it altered to fit?

The shoulders probably won't fit, and the alterations will probably make it look odd/off-balance. Whenever people post pictures where they've done this it looks just horrible.

Don't do it.

No and no...did I say no? I meant no.

You God Damm Right You Shouldn't!

If the trousers are too big, they can usually be altered for much less. If they are grossly oversized, like 6" or more, I am not sure since I haven't had that done.

This is generally true since the big problem you'll get with 4"+ slimming is that the back pockets will be too close (or even meet - ugh!!!).

My understanding is that this can be solved if you have the tailor essentially "re-cut" the entire legs of the pants, but this is surgery and - depending on the tailor- risky.

Very Bad Idea!!!

Is this a bad idea? YES
They might be able to make it look like a Zoot suit or like you're wearing dad's suit to the school dance

If the shoulders fit a good tailor can do alot of alterations - but of course this will also cost a considerable amount of money. So don't buy it

Unanimously, do not pursue this endeavour. It would be a sheer waste of money. Buy a suit in your size.

What's the point of buying RLBL if you're changing the whole suit?

There's always another one in your size available on Ebay, eventually.