Is it possible to pay just £500 for priority service for whole family?

Dear all, I am just wondering about this in case someone wants to try this or someone has already tried something similar. I know that if a family of 4 (main + 3 dependents) apply for ILR (Set-O) together and want priority service, they have to pay 500x4 = £2000 for 5-day priority service.

In an effort to cut costs, would it be possible for the main applicant and 2 children to apply together and opt for standard service, and then the partner/wife/husband to apply separately few days later and ask for priority service by just paying £500? If the UKVI honours this request, then they have to make a decision within 5 days for the main applicant before they can decide on the partner/wife/husband. I am not sure if UKVI will honour this but there seems to be no harm in trying. If they honour this, the family will potentially save £1500.

If the moderators or anyone else could share their experience, this could be helpful and potentially save money for so many. [I won't personally benefit as I just got standard service approved for the whole family but the wait was too long 2-3 months].

It doesn't work like that.

UKVI will hold the dependent priority applications as standard service pending the main applicants decision based on standard service