For the Self Propelled Artillery, the ability to use "Land Mode" that the main guns on the cruisers enjoy, would make it so much easier.  Our current SPG doesn't have that option, which makes it kinda useless as artillery.
Now don't forget this:
SdKfz 124 Wespe "Wasp"
Type    Self-propelled artillery
Place of origin     Nazi Germany
Service history
In service    1943 - 1945
Wars    World War II
Production history
Designer    Alkett
Produced    1943 - 1944
Number built    662
Variants    ammunition carrier
Specifications
Weight    11 tonnes (24,250 lbs)
Length    4.81 metres (15 ft 9 in)
Width    2.28 metres (7 ft 6 in)
Height    2.3 metres (7 ft 7 in)
Crew    5 (commander, driver, three gunners)
Armor    5 - 30 mm (.19 - 1.18 in)
Primary
armament    1x 10.5 cm leFH 18M L/28
with 32 rounds
Engine    6-cyl petrol Maybach HL62TR
140 hp (105 kW)
Power/weight    12.7 hp/tonne
Suspension    leaf spring
Operational
range    220 km (137 mi)
Speed    40 km/h (25 mph)
Then we could add the Sd.Kfz. 234/2 "Puma" for sure.  
