Ajax Self Propelled Artillery
The Ajax's engine is potentially a problem with the amount of heat it emits. Many proposals to address this have been suggested, and one, which more or less consisted of 'just remove the top armor from the engine to let it air out better', has been taken to quite frankly some excessive lengths with how it developed.
The Ajax SPA is a result of the development of said proposal, and would be the second in the Ajax family of fighting vehicles. Quite simply to start, the Ajax SPA completely removes not only the top armor of the tank exposing its internals to the skies, but the turret entirely, as well as two of the machine guns. The main gun (modified slightly to make it more suitable to the role of artillery) is moved to a mount on the hull, with capabilities for much higher elevation than its predecessor's turret. The side and rear armor is thinned greatly, enough to provide protection against small arms and heavy machine guns, but not enough to protect against serious anti-tank weaponry. The front armor however, remains just as formidable, rendering it a challenge to any foe forced to fight against it in a head-to-head scenario and making direct fire missions not suicidal for this still massive vehicle.
Overall, between the improved engine and crew ventilation, a fire extinguisher, and a solid physical barrier between the crew area and the engine, it is hoped that the Ajax SPA is capable of utilizing the original engine of the Ajax AFV, although despite the lighter weight of the SPA, due to the nature of said engine we don't expect much improvement in max speed beyond the AFV's original parameters.