Client requesting data to be not split into multiple sheets in excel or rtf template

Summary:

Our client is requesting that the output does not be split into different sheets if the count of records are more than 65K in Excel and 1M in RTF while generating excel output. Is there a way around this? Since there is a benefit of 35K in RTF layout compared to the Excel layout, client is insisting on changing the excel layouts to RTF template even for reports that has more than 63 columns. We are trying to convince that there are pros and cons to using the excel layout for large volume reports and it gives additional columns space