Mostly anyone can be elected to a strata committee, provided they are nominated by an owner who is not standing for election. The exceptions include the building manager or a real estate agent who operates in the block, and who are not owners.
In the first few years of our current building, the architect was on the committee, which was utterly invaluable. And the good news is that if the owners realise they have “accidentally” elected someone on to the committee who really shouldn’t be there, a simple majority can vote them off at a general meeting.
A non-owner can’t elect themselves on to the committee, unless they carry a valid proxy from an owner.