[Tool Update Request] - Custom kernels in VariBlur/Defocus

Any chance of seeing custom (scalar+rgb) kernel support for these tools ? Or a general convolve node ? Its something I've been using in Nuke on every single shot. From look-dev tasks to lens convolutions and flares. But a decent start would be custom kernels for the VariBlur and Defocus nodes.
They are just straight up convolution matrices right ? Cause I don't see any side-effects of any FFT magic , which should speed these rather slow tools up.
They are just straight up convolution matrices right ? Cause I don't see any side-effects of any FFT magic , which should speed these rather slow tools up.