I dunno I like this. I feel like it's balancing by making it harder to use and not just by making it less effective.
It's not really making them hard to use. It's moreso cutting down viable setups. The only 8 charge at once setup that will be viable is a linear choke point setup.
For example, let's look at two possible setups on Burning Paris:
Set up 1: Setting up in the second floor of the hotel, putting a line of 8 charges down the long hallway.
Set up 2: Setting up in the spawn area, placing 2 charges covering the bar, 1 covering the catwalk, 1 in the doorway of the building under the catwalk, 1 covering the tunnel, 2 covering the hotel entrance, and 1 covering the rubble to the left of the hotel entrance.
The second setup isn't going to be viable at all with the strictly linear detonation sequence. If you want to use 8 charges at once you'll need to camp in a long hallway with one entrance that the majority of zeds will come through.
With the ability to control how you detonate the C4,
the first setup doesn't become any stronger than it already is on a linear setup. However, the alternative and riskier setup of holding out in the spawn suddenly becomes viable.
Chokepoint camping will not be made any stronger than it already is on a controlled demolition setup. It only allows non-chokepoint camping to become stronger, even if it will still be weaker than chokepoint camping.