You cannot avoid adding an owner unless you register the vehicle in trade, this then means you cannot tax it especially if you don't have the V5 as you won't have the code to do this, therefore you if you put this in trade you cannot take it on the road unless you have trade plates, you then would need trade insurance to be able to drive using these and check that they cover this (most do but always check)
You used to be able to pay for tax even when the vehicle was registered in trade but they have since stopped this, I spoke to DVLA about this recently and they have said it cannot be done unless you provide the V5 number on either slip or tax reminder to tax the vehicle, once the owner is updated to trade the log book becomes void until the new one is sent out, this is what DVLA told me, unless someone on here knows a cheeky way around this, there is no way to avoid adding owners unfortunately unless you have space and trade plates.