Remember that lifts are regulated by law.
Whilst what you suggest ie manufacturing spare parts is feasible, you would find it hard to find anyone to “stand by” such a fix, considering there are severe penalties for both the lift owner (you) and the maintenance company should an accident occur.
Lifts are expensive, but so are the penalties for not maintaining them.
You can always get a second or third opinion from other lift maintenance companies, but if any of them are recommending upgrade or replacement, you’d be wise to heed their advice.