hm. looks like a logical flaw again. shame on me
while a tech player suffers a malus on using magickal equipment (the bonuses of the items go negative
(there was a thread here stating this, can't remember where), making them inferior to regular equipment of equal value), and tech items carry hefty maluses for mages (the gun from the Vendigroth schematic had a 85% chance of crit fail on a 100 MA character

), a magick-tech neutral (or low-tech) player will be able to use a high-tech item without any disadvantages of lacking tech aptitude (TA).
(I'm actually not too sure here. IMHO having low TA will cause high-tech stuff to crit-fail too. does anybody have low-tech high-level chars and spare time to test the crit-fail chances on that Vendigroth gun?)
while this is absolutely real - you don't have to know chemistry or physix to pull the pin and throw a grenade

- it makes my plans unbalanced.
but maybe this can be solved with the introduction of use+maintenance expertise, as The_Bob suggested.
I'm sorry to deviate into hardcore theoretical modding again, but that could look somehow like this:
a character has crafting expertise, derived from the college in question and IN + manuals, as it works right now. thus being smart allows you to craft stuff by following a manual, while u lack the knowledge and experience on using the crafted item under combat conditions.
the character then has use+maintenance expertise, derived from the colleges and skills to which the item belongs (i.e. firearms, gunsmithy and chemistry for flamethrower; melee, smithy and electrix for charged axe) and from the character's TA and IN. this expertise should influence the high-tech items in a similar way as MA influences spells - a master swordsmith will more or less fail with a flamethrower. a master chemist / demolitioner will do better due to experience with ranged combat and fire. but the full power of the said flamethrower is reserved for a master gunner-gunsmith-chemist-demolitioner who has understood and mastered
all the principles of the weapon's operations. (assuming A:WIP or Carcanum in play and levelcap of 100)
as a slightly more realistic approach - is it possible to expand the mage-tech aptitude from 100-0-100 to 300-0-300? or maybe make individual spells / skills / tech colleges contribute less to the scale?