Approx 5 years ago I joined a company with machinery that pre-dated PUWER by a couple of years and lacked guarding. Lots of rotating shafts and belts at high speeds.
Between accepting the job and starting there was a serious accident, (the weekend shift before I started), which caused an amputation. So I walked straight into a major HSE investigation on day one.
The management team thought their machinery was OK, because this was the first serious accident in 16 years, but I very quickly found out the opposite. It turned out the previous production manager had removed alot of guarding and what was left, he had removed the interlocks from as they slowed down production. Which the HSE investigation also discovered as they started interviewing people.
The outcome was a prosecution and hefty fine for a breach of Reg 11 of PUWER and 2 improvement notices (the first for "Access to the machine has not been prevented to the extent so far as is practicable", and the second for "Insufficient Risk Assessment" because the RA had not identified the part of the machine that caused the injury).
To this day I do not know how the HSE did not issue a prohibition notice, there was a significant lack of guarding in that plant. I believe the inspectors took pitty on me, as it was my first day and I was able to convince them that I could work with them to bring the level of safety up to a level that would satisfy them.
The action plan involved re-risk assessing the whole site as it quickly became apparent that none of the RA's were sufficient, which took a team of four assessors 6 months to complete and a full guarding audit, with a plan including funding to bring the plant up to standard. All of which were in the included in the requirements of the improvement notices.
I met a lot of resistance about adding new guards, but I worked with the operators, involved them in the design process and got them to accept it with reluctance. The guarding took 18 months to design and install, but because operators were involved with the guarding designers I had their buy-in. Their was slight dip in outputs initially, but they were quickly back up to the same levels.
Therefore in answer to your question, I would not be worried about OHSAS 18001. The consultant is right, get the guards in place, but design them so that they are both protecting the hazard, while not getting in the operators way and get the operators involved with the design.
There is no point looking at OHSAS 18001 until you have the basics in place. Without the basics in place you are exposing operators/technicians/engineers to hazards and if it should go wrong it will have a big impact on individuals lives and the company.
In the case I reference, the fine was small in comparison to the capital expenditure on guarding, (over £250K), the civil claim for the injured person, which to date I believe still has not been finalised, but interim payments made to date are more than double spent on guarding and not forgetting the affect the injury has had to the life of the injured person and their family.
This was a large multi-national company and the site in question employed nearly 300 people with an annual turnover of £125million. An incident like this at a smaller company could be the end of that company. I know of one profitable manufacturing company that had a fatality on unguarded machinery, which 3 months later found itself being liquidated as the prohibition notice meant they could not meet orders and therefore the cashflow dried up.
Therefore just because there is a good track record, does not necessarily mean the same for the future if you have machinery of the nature you describe.