Bitcoin script is purposefully not turing complete-- it's not an accident, in fact it's extremely easy to be accidentally turing complete.  Turing completeness provides no value for this application and creates additional risks.  Helping someone make a bitcoin clone turing complete is like 'helping' them have an infinite coin supply.

There are plenty of limitation in script that are make it less useful, but lack of turing completeness in the script language is not among them.