Aside from purely combat-related problems that aardvark outlined (well, I personally would not place a certain bet on a space marine against an ascended character, and survivability whilst refraining from combat is not an issue) you will have a purely roleplaying one, namely - social interaction.
While the rest of the party are god-like warriors to be feared and all, you also have a human nearby - someone who isn't feared to talk to, and someone who propably will have tons of peer talents to further complicate matters for GM.
I think that a house rule is possibly the best answer, barring some detail in the RAW that is being missed.
Simple Rule: as the distance thrown doubles, double the scatter. If a 30m throw is a 5m scatter, a 60m throw results in a 10m scatter. Thus for Space Marines hit they have to get it right or throw a larger grenade with a greater blast radius.
Complex Rule: Mathematically determine the cone of scatter as distance extends. Account for hallways or other constrained spaces, e.g., a 40m hallway 3m wide with target at 30m. Account for roll in the scatter (What is the shape of the grenade? Has the user modified it to not roll, spikes or other roll retarder?). Account for overpressure in confined spaces.
I'm not prepared to write the house rule because I'm not sure how crunchy your game is or how crunchy your players like rules.
I might find a common sense middle ground, accounting for confined spaces in scatter and rolling grenades, but drop the math and overpressure damage and just reduce damage by 1/2 on a miss where scatter was called for, at least in confined spaces. In exterior spaces I might reduce damage to 1/4, if it made common sense.
A 1000m throw, while Space Marine's power armor is quite powerful, is something as a GM I may laugh it, but still say,"Yes, but ... you need to strap some kind of booster to it or "over clock" your power armor in some heretofore unknown method at a cost of possible rotator cuff damage to armor or body or both" :) But sure, you can throw it a 1000m. Roll at an -50% to hit and roll X for armor damage and Y for physical damage. If there was some "indirect fire rule" I might invoke that (certainly in the case of a grenade with a booster rocket, but why is the PC considering such an action anyway? Just get a mortar from the chest... Oh wait, different movie).
<evil-gm-laugh>Bwahhahahahahah.</evil-gm-laugh>
Best Answer
I would say NO.
The Servo Skull is a hollowed-out skull, the brain is only held "working" by a cogitator, and the AI is the one that is controlling the skull. It might have some resemblance to its previous owner, it might even feel "haunted" by his spirit, but the object itself is just a robotic utility.
You will have as much result with as putting Vox on a vending machine, a rifle, or a toaster. That is to say, nothing -should- happen, if everything follows the basic rules of nature.
But as with all things, everything is up to the GM in the final say.