perhaps the most glass cannon without being a spg but a poorley made tank destroyer. it would have perhaps a br5 gun while have br2/3 armor. lacking any mg this would be an allied marder class. good if you got the first shot on another tank or could scoot and shoot against infantry.
You can find this tank in War Thunder already.
It would be similar to the german Flak Bus anf would thus sit at BR4. Good gun but (very) open top and no particularly good mobility.
Flak bus still needs to move to BR3, it really doesnt have a right to be BR4, especially when vehicles like the dickermax which are significantly more covered sit at BR3.