Thank you for pointing out some additional risks.   It is extremely important to quantify everything with dollar amounts.  I used to write business cases for just these types of situations and used monte-carlo simulations to quantify risks.  I'm retired now, but you can easily find MC models that plug into Excel. Start at costs and then work the risk situations into the analysis.  Don't make recommendations, just perfor. The analysis.  

All you should have to do to get your management's attention is point out the high cost of failure and how very likely failure is to happen (complete shutdown and replacement of servers and associated equipment along with the AC). .  The cost of downtime alone could kill the company.  Look at Delta and the effects of the Crowdstrike shutdown.  I would use that as the example in your report.  They are suing CS and Microsoft for hundreds of millions of dollars.

Writing a business case is key.  Describe what happened, what the current situation is , and the two choices for fixing the problem.  Gather cost information and use hard numbers wherever possible.  

Print hardcopies of the report and distribute to the executive team.  Make a summary PowerPoint presentation.  Sell your solution.  If nothing is done and the inevitable happens...well, not your fault.