Thickening cream in a blender to increase fat content? I've established that it's not possible(or a compromise at best) to mix other things in single cream to increase its fat content.
I have 25% and 30%(rarer) cream available where I'm at, and I'd like to have whippable cream with a fat content of 35% or more to use in homemade ice cream.
I've considered and rejected the following methods already:

Adding gelatin. This recipe is vegetarian so gelatin is not an option. I have not tried agar-agar or carrageenan yet.
Mixing butter in the cream or whole milk. This'll lead to a grainy ice-cream so, no.

Is a blender or food processor an option? If a cream can be thickened using a centrifuge, will a blender be powerful enough to thicken it by separating out the buttermilk?
If not, what else can I do? Heating the cream on a low flame?
The centrifuge doesn't thicken the cream by mechanical action, but by separating the fat and water by their different densities.  The blender allows- not until solid but until ice crystals form,  you to spin, but not to draw off either liquid.  There's a chance that when allowed to settle you'll get layers, but you're more likely to make butter so you'd have to stop just in time, then let it settle.
It might be worth experimenting with freezing the cream and then allowing it to defrost in the fridge without stirring.  This should break the emulsion and cause it to separate, hopefully into layers.