There is such a transform power in USPD and this was part of my dislike of the +1 amicable modifier for the summon method. They used a limited target (spare parts) -1/2. One thing about the transform method is that it is cumulative so a power with expanded class can be built for relatively few points - it just takes more time to get the results wanted. That makes the trasform method even more potentially abusive than the summon method. At least the summon method defines the maximum points of the summoned machine. The transform method is limited by body only and the cumulative affect means there is no upper limit on results, especially with expanded class modifiers.
Obviously the GM has to be vigilant in both cases but why should one method have to pay extra points for "amicability " that the other method gets for free? Or in the case of common machines why should one method have to pay for loyalty it does not receive when the other doesn't have to?
Player: "I transform those two cars into one car with 15PD defence and security system that only responds to my voice command"
All the player has to do is perform the transform out of combat and there is no upper limit on what can be made. Again the GM has to think hard about that power.
At least the Summon method has built in point limits, which I think it is preferable over transform. The control over the power is more tangible for the GM and puts less demands on him/her to keep it under control. And potentially less motivation to just ban an interesting power outright.
But the player or NPC should also get what they pay for. Common objects cannot give loyalty. Just ask a pet rock owner.
By the way I build characters for fun and GM. So I have no personal motivation in terms fo building a character I will play. I am just interested in making more sense out of this power construct.