They can probably find other gigs to fill in this space. It's not like they have sail along with the contracts they have till retirement. Any underemployment after a point is their own fault and/or their agency's.
I'm still trying to work out what purpose these women serve in the race itself other than having more adverts plastered on them. If we're gonna play the employment card... why not have grid guys serve alongside the grid gals? After all male models also need employment opprotunities.