Wealth alone is not a sound basis for selecting the principal applicant. The legal and household circumstances of the proposed people need review.
Separate payer from applicant choice
Explain who owns the proposed funds and who seeks permanent residence, then ask counsel to assess the arrangement. Check how the spouse and children would be treated under the current programme. Do not rearrange the application merely to match an account name without understanding the legal and family consequences.
Separate the choice of payer from the choice of applicant, since they are different decisions and the wealthiest family member is not automatically the right principal. Assess each candidate on their own history and circumstances, then consider which arrangement best serves the household as a whole, including who would derive status from whom and what would happen if the principal's position changed. A family member with substantial assets and a complicated immigration history may be a worse principal than one with neither.
Where the payer and the applicant differ, document the arrangement between them properly and take advice on how it should be recorded. Have this conversation before any assessment is commissioned, since it determines whose history needs examining first. Record the reasoning behind whichever choice is made, since circumstances change and a decision that was made deliberately is far easier to revisit than one nobody remembers making.