Allow more specific input blocks to inherit from generic ones

[HarryCutts]

In the input section of my Sway config, I want to do two things: customize my keyboard settings (layout, xkb_options), and disable acceleration for Trackpoints. This seems simple enough when I just consider the Trackpoint built in to my laptop:

input "type:keyboard" {
    xkb_options caps:escape,shift:both_capslock,compose:ralt
    # ...
}

input "2:10:TPPS/2_Elan_TrackPoint" {
    accel_profile flat
}

...however, on my desk I have a keyboard that includes a Trackpoint, both reported with the same device name and identifier. If I add the same input block with accel_profile flat for that keyboard, it resets the changes I made in the input "type:keyboard" block. So at the moment I have re-state everything for that keyboard:

set $xkb_options caps:escape,shift:both_capslock,compose:ralt
input "type:keyboard" {
    xkb_options $xkb_options
    # ...
}

input "2:10:TPPS/2_Elan_TrackPoint" {
    accel_profile flat
}

input "7504:24866:Ultimate_Gadget_Laboratories_UHK_60_v1" {
    xkb_options $xkb_options
    # ...
    accel_profile flat
}

It would be nice if there was some way to make the last input block inherit the options from the more generic input "type:keyboard" block, maybe by adding extend or also before the {.