I would like to suggest the Geschützwagen Tiger, while it is allready passed for concidderation, it doesnt hurt to have it also here on the new forum.
It was build after long development time at the end of ww2, to get the 17 cm K. 72 L/50 and 21 cm M. 18 L/31 in a mobile form on the field, but also to dismount it and use it as an ammo carried which was also its downfall, as that ability with the requirement to use the full unmodified Mörserlafette 18 which can carry the 17 cm K. 72 L/50, 21 cm M. 18 L/31 and 15 cm Sk C/28 L/55 (All 3 guns were used as production of the 17 and 21 cm guns alone couldnt keep up with the demand). This increased the required space, hindered the capabilitys and increased the weight.
Overall The Geschützwagen Tiger is based on the Tiger II Hull, beeing extended, placing the engine in the middle and reducing the armour to a minimum. With the Hull front beeing 30mm superstructure 16mm at an angle as well as the sides and rear beeing 16mm.
It can go up to max 45 kmh with the HL 230P30 engine limited to 650Ps/2500rpm and overall weight of 60 tons.
The Ammo would be 5+1 of 17cm, 3+1 of 21 cm and 7+1 of 15 cm, this could however be artificially increased by the addition of an ammo trailer (like on the Chi-Ha LGs ammo box at the back which wasnt there IRL).
The 17 cm K. is also known under 17 cm K. 18 L/50, 17 cm K. 44 L/50 and of course 17 cm K. 72 L/50
Traverse is 5° to both sides each and elevation is -2° to +48° (17 cm) +50° (15cm) and +68° (21cm)
I suggest all guns possibly as modifications as depending where the G.W. Tiger is placed considdering that its pretty much a Glasscannon/Much cannon with few metal around it, the performance in guns isnt that important, because it will certainly go through.
Performance of the Guns:
17 cm K. 72 L/50:
Pzgr. 43 Apcbc 71 kg 2,345 kg filler 850 m/s with 303mm/10m penetration
K.Gr. 39 He 68 kg 7,33 kg filler
21 cm M.18 L/31:
Gr. 18 Be Sapbc 121,4 kg 11,5 kg filler of Fp.02 und Np.10 (14,72kg) 550 m/s with 156mm/10m penetration
Gr. 18 He 133kg 17,35 kg Fp.02 550m/s
15 cm Sk C/28 L/55: (Like found on Admiral Graf Spee)
Pzgr. L/3,7 (m.Hb.) Apcbc 45,5 kg 1,1 kg Fp.02 875 m/s 283mm/10m
Sprgr. L/4,5 Kz (m.Hb.) He 45,5 kg 3,64 kg Fp.02 875 m/s 37mm/all
Sprgr. L/4,4 Bdz (m.Hb.) Sapbc 45,5 kg 3,03 kg Fp.02 875 m/s
Panzer Tracts No. 10
H.Dv. 481/41 Munition des 21 cm Mörsers 18
H.Dv. 119/562 Schußtafel für den 21 cm Mörser 18
H.Dv. 119/484 Schußtafel für die 15 cm Kanone in Mörserlafette