As no good deed goes unpunished, so no good idea goes uncriticized (See my post of March 23, 2009: pros and cons of various practices, with 13 references and two metaposts.). Although I like the idea of a law department designating core staff at a firm, I can anticipate objections to the practice.
Core staff have less opportunity to learn new tricks from other clients.
They may not have enough work to keep fully busy, so their time betrays some padding.
The lawyers themselves may not want to specialize to that degree in you or your matters.
The core staff may not get along well as a team.
Your department could be micro-managing operations of the firm (See my post of Aug. 4, 2008: interventions with three posts and 40 references.). Or see my article, “When Interventions Go Too Far”(NY LJ., Feb. 28, 2008)
With the inevitable attrition of associates, you lose bench strength and backup.
Notwithstanding these risks, I endorse the practice of law departments choosing a small group of lawyers (and paralegals) to work on their matters.