Despite the shared SDR designation, the
Venom is as much a separate 'Mech from the
Spider as the
Grand Dragon is from its own parent design (or arguably moreso, since the latter pair are at least the same weight) - and note how no
Dragon variants (including the Hero 'Mechs) allow for the
Grand Dragon setup.
That being said, there are a couple of potential heroes for the Spider:
"
Lieutenant Gwndolyn Snedicor: Recently promoted to command a strike lance in the 151st Dark Horse regiment of the Eridani Light Horse, Gwndolyn has shown a talent for both reconnaissance and raiding but is still new to issuing commands. Suffering from severe arachnophobia, she finds it ironic that she was not only assigned to a
Spider and has talent using it, but she has also been at the forefront of the unit’s run-ins with Natasha Kerensky."
"
Captain Rhonda Stillston: In charge of a recon company in the Addicks Draconis March Militia, Captain Stillson has been a force to be reckoned with on the Combine border for over two decades. Easily recognizable in her bright red
Spider with gold highlights, she won’t hesitate to engage units twice her ’Mech’s mass, using her superior mobility to hit and run. Being on the short list for a promotion to major has curtailed her ferocity to some extent, but her company helps keep her on top of the enemy at all times."
Both are listed in TRO 3039 (on page 106), and neither lists the specific loadout of the 'Mech itself... which could give PGI the leeway to (mostly) emulate the
Venom's loadout on an actual
Spider rather than a heavier (albeit related) 'Mech, and attribute it to an apparently-notable canon character.
And, yes, it should be doable...

Chassis: Endo-Steel
Engine: STD 180 (base max speed of 97 kph)
Jump Jets: x6 (LT, RT, x2 CT, LL, RL)
Armor: Ferro-Fibrous (5.5 tons, 194 armor points (92% of maximum))
Heat Sinks: x10 DHS (7 in engine, x2 LT, x1 RT)
Weapons: x4 MPLas (x2 LT, x2 RT)
All tonnage and criticals used; tested in RemLab