Cool stuff, can't wait to see what you got.
Also, here's my crack at a 70 ton TL10 MBT, note I used my Structural Reinforcement rules for it since I worked on this before your reply and my HR on APEP rounds that brings them more in line with the ammunition modifiers in High-Tech and they only increase cost by 7, not 10 times.
It has 1 110mm main railgun, 2 15mm point defense railguns and the ability to hold a drone that weighs up to 1.2tons. It's driver section has two holographic workstations and a C6 mainframe. At the rear it has two more holographic workstations for the drone operations crew.
It's frontal armor is made of two layers of Diamondoid Laminate sandwiched between three layers of Advanced Nano-Laminate and counts as having double dDR vs shaped charge and plasma attacks. The rest of the tank has conventional Nanocomposite.
Other then this, it follows the basic plan of your 100ton MBT.
Code:
TL Vehicle dST/dHP Hnd/SR HT Move LWt. Load SM Occ. dDR Range Cost Loc. Notes
10 70ton MBT 26/42 -3/5 13 3/30 70 1.6 +5 2+2SV 233/45 504 $12.2M 2C1T2t [1]
[1]Has dDR 233 on the front vehicle arc that counts as laminated, dDR on the sides, dDR on top, dDR 25 at the rear, and dDR 20 on he bottom.
The 110mm main gun does 7d×8(3) pi++ dDamamge, and has range 17,000/130,000 with APEP or 3d×11 pi++, range 8,600/65,000 with basic ball ammo. The cannon has ROF 1, ST 71M, bulk -13, rcl 3 and holds 133 rounds that weigh 53lbs each.
The two 15mm point defense railguns do 4d+2(2) pi dDamage, and range 100,000/250,000 with APEP or 2d+1(2) pi dDamage, range 50,000/130,000 with basic ball ammo. The guns have ROF 20, ST 49M, bulk -11, rcl 2, and holds 120 rounds per gun that weigh 30lbs each.
Note that the 30lbs per shot for the point defense guns came from running the number with how Spaceships scale things, I personally think that's kinda overkill heh. Also the range figures a semi-fudged. I run some funky numbers to get my EM gun spreadsheet to give me rounds that would weigh as much as what Spaceships lists and the variables effect range. They're probably not too far off though and as you can see, the ranges at a point they almost don't matter in ground combat.