Instanced object overall brightness from ground's lightmap value

One problem I’ve noticed is that when scattering a large number of 2d plants and bushes, if I enable light maps then the bake takes forever, and as I understand it performance will also take a hit in the browser.

To avoid objects with no light maps appearing bright when in shadow, would it be possible to have a “brightness from object” option in the objects panel, where you could choose another object for this objects overall brightness to be multiplied?

So say for example I have a tree on a huge ground, it could have it’s diffuse map multiplied by the nearest lightmap pixel of the ground object.

You could maybe even automate the process by baking the large objects first, and then before baking the smaller objects, check if the object they’re directly on top of have sufficient variation in lightmap pixels directly beneath the object to warrant baking the smaller objects lightmap, and if not, then revert to multiplying the small objects diffuse by the lightmap pixel of the object it’s sat on instead. The distance checked along the large object would need to be proportionate to the small objects height and the light direction perhaps.