Because an orbit is a balance of forces, it has a very specific path, a reduction of gravity with no other change would result in the path of all things orbiting, outwards, due to their centrigugal forces throwing them outwards, becoming greater than the reduced gravity pulling them inwards, they would fly off into space.
This is why we need to be so careful of GeoEngineering, ie don't do it at all.
Solar pressure also has to be a component of the forces in balance. Increasing solar pressure on Earth, by increasing its reflectivity with no other change, has to result in a change in the path followed by Earth, outwards. However small, that change is magnified nonlinearly by the corresoonding reduction of gravity, which is related to the change of distance as an inverse square law.
We could be heading off into space in only a few years after GeoEngineering, there would be no way of reversing its effects.
This is why it is so scary, the power to do things like this lies in the hands of investors, and yet mostly they don't understand the deeper consequences of some potential investments, made with the best of progressive intentions, the phenomenon and power of capital could be the end of us.
This is another reason we need to move to Kardashev Money asap, before investors do something even more damaging than has been done already with their capital.
Kardashev Money will remove that power from the minority, distributing it amongst the majority, who instinctively know better what is good and not so good, it seems to me, not because it is any reflection on the hearts of whale investors, but because the presence of caoital makes our minds lazy, we don't realise our thinking becomes lazy, we can't be bothered thinking to deeply, when we no longer have to.
Your question shows you have not got that lazy mind, you are thinking deeply enough to ask that really important question :)