I believe that aeroplanes certified single pilot but operated within company procedures 2-pilot still only need CPL/IR.
That's correct. You can operate aircraft like CitationJets and Kingairs commercially with two CPL/IR holders. But the main problem is to find employment with only a CPL because there are thousands of unemployed ATPL holders queuing for every job opportunity - why should anyone employ a pilot with lesser qualifications (unless for financial reasons)?
Go for the full ATPL, it is worth the extra effort.