If any issue in case we apply PurchasingSide T/C only?

Dears,

My client is a manufacturing company who purchases raw material from both future exchange and local fixed vendors.

In case buy the future, it has to activate GTM but only purchasing side T/C is required. In such case, will be any issue if it only has purchasing T/C which can not do the assosiation with sales side T/C? and if we have to swith between GTM T/C and logistics contract for different purchasing model?