I think you should be able to loan drivers/staff from another team in your league (with both managers' permission of course).
The length and cost of these loans could be decided manager-manager through league wall, mail or Discord etc.
For example,
Short term loan- 1/2 a season-1 season
Long term loan- 1-2 seasons
Price could be between 1 and 10 tokens. The longer the loan, the higher the price.