Maybe something like:

Sure, you can do it like that [that way], but what you['ll] get [end up with] is [just] crap.

@ Reinhard W:
Sorry, ich sehe hier nirgends eine Frage, auf die dein Posting eine Antwort gibt... daher mein Tipp: unkonstuktive Kommentare kann man sich auch gerne mal klemmen...
@SD3: Super, danke! Klingt viel besser als meine Übersetzung!
Trotzdem bin ich für weitere Vorschläge immer offen

'Course you can do it like that, but then it'll be crap, won't it

(oder, für den höheren Grad an Umgangssprache: innit ;-)

innit only works for BE -- or is at least rare in AE.

Gleiche Kerbe:

"Sure, could be done like that, but it's gonna end up shitty."

What is "it"? The appropriate translation will surely depend on the activity being referred to.

#2+4 sound fine to me. I wouldn't use #6's "end up shitty", which simply doesn't sound idiomatic.

@all: thanks a lot!
"it" is meant to be a poorly performed technique in sports. i guess these examples work in this area of application :)