Why an LPD hull is difficult to turn into an escort

Could a viable surface combatant be built on an LPD hull?

The size is attractive, but the hull and propulsion would need major work to reach the speed required to escort an aircraft carrier.

An LPD offers attractive volume for weapons, sensors, and support spaces. The difficulty is that an escort must keep pace with an aircraft carrier. Amphibious hull form and installed power are not normally optimized for that speed. A conversion would therefore require substantial changes to the hull and machinery instead of a simple combat-system fit.