When I'm owning someone in every way I let him/her transform kuz I'll keep owning this person in the same way but gaining more pl.
If I consider a person a threat for me I'll be in this person's way much more often and I won't let him regain ki, charge attacks or transform, I give this person
war.
If I consider a challenge that a person transforms then I will hesitate, but a person like that usually has the skill to outrun me and surprise me once he has transformed already. But for those who stop rigth in front of meh nose to transform just dosen't make a challenge for me at all and I have a lotta fun kickin them around.
Someone mentioned that in the show they don't interrupt a transformation, well that's usually because they are affraid and can't do **** (like when frieza transforms) or they are being foolish (like when vegeta lets cell absorb a18). ESF is a game and a very free one, this means that you can do things however you would do them if you were really there and you don't have to follow any rules based on how the characters act in the show, this is because we have a
personality 
*Beware* -this last mentioned word may sound strange to weak individuals causing secondary effects as a minor headache-
Also someone said something I liked "Transforming is a privilege and not a right".
Now I'm not justifying beam whores who
gain pl by transkilling and spirit bomb or SBC spamming, these are noobs.