You've made two key changes:
- Allowing multiple combat half-actions per round
- allowing movement to be replaced by a non-movement half-action
The primary factors I see are:
- increase in Psyker offensive capability (Most of their offense is more powerful than their allowed weapons; it gets worse under RT or DW, due to a different psychic system)
- decreased access to defenses¹
- decreased emphasis on movement²
- increased emphasis on non-action defense (IE, cover)³
- breaks the equipment bonuses
- decreases incentives to use burst and full-auto autofire modes
- cybernetics and talents with extra half-actions become devalued⁴
- initiative becomes more important⁵
- Ganging up becomes less essential⁶
¹: Since one gets very few defenses per turn, this change of yours makes them less valuable, by allowing them to be overwhelmed faster.
²: The current system makes movement a valuable and essentially irreplaceable part of the round; take it or not, it's lost if unused or unusable. It's not terribly realistic, but is very cinematic. And DH, RT, and DW are all intended to be very cinematic in tone.
³: At present, especially for melee, active defenses (dodge and parry) are quite valuable; cover is less so, but not enough to render it useless. When one allows replaceing movement with a second attack, cover suddenly becomes MUCH more attractive, as it's an assured penalty to be hit, instead of a roll by the defender... but it also reduces drama.
⁴: At present, the only way to get a second attack is expensive talents and/or cyberware with inexpensive talents. If a character can just hole up in cover and double shoot, these talents are far less valuable, making the Assassin and Guardsman's additional combat actions less useful.
⁵: Further, by allowing the etra attacks, you can run a target out of actions sooner, as well, so initiative becomes more important to prevent having actions drained in defenses.
⁶: Ganging up is the great equalizer in RT and DH combats; it's how one overwhelms defenses. Given that every character can defend once for free, and once by aborting, if you can attack twice, you've just eaten both defenses this round, meaning you only need one attack from a buddy to get through. The norm is that you need two buddies to negate the defenses, or one buddy with a multiple attack talent.
It sounds like you made these changes with rank 1-2 characters... it's going to be more profoundly off-norm or higher rank characters, as normal slow growth of actions is made to feel even slower by providing far less of a bonus over not having them.
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.
Best Answer
There will be two attacks. On page 190 of the main rulebook, under the Full Auto Burst heading, it says that if you have two pistols in your hands you may fire them both. Page 197 discusses two-weapon fighting, and while it doesn't explicitly say that you make two attacks, note that two-weapon fighting with a melee weapon and a pistol does call for resolving each attack separately. Also, there's no stated bonus for using two weapons other than the potential for two attacks, which strongly indicates that you get to make two attacks -- otherwise, you'd never do it.
As a sidenote, also per page 197, you may only lay down one area of suppressive fire even with two full automatic weapons.