Due to personal characteristics I view the actions of 3/4 of the grands i have played on as too heavy. I'm sorry I'm not a Prussian or Russian, but there it is- i like playing piano but am not built to play a full concert grand in a 2000 seat hall. I'm built native Am. - built to run deer to exhaustion with a spear over wet rocks, not plow fields with an ox or reef heavy sails.
I was talking to a local minister who had the same problem: she is a 50 kilo female, previously the church musician, and received as a donation in a previous parish a Steinway grand that was too heavy for the purchaser. It was too heavy for her, too. By contrast, I played a store brand grand last week that was fine. So they do make grands with tolerably light actions.
Within limits it is possible to swap whole actions in minutes. Pianostreet has an article on a grand at a NYC venue that comes with two actions available for different artists.
I wouldn't monkey with modifying a new very expensive name piano action like a Sauter. I'd buy some other lesser known grand, throw away the case and swap the light non-professional action in. That way if you have to resell due to downsizing or moving to more expensive city, the original action can go back in. The piano for sale would be original, with the original action.
There is a $300 grand for sale near me that would be a perfect donor for this sort of graft. It is a no name brand from 1937 , there is no market for it, but it has low hours and works fine. The tone is a little bland I imagine.
You have to take careful measurements of the action mount points to prove this is doable but a tape measure should suffice I would think.
Your tech may not like this idea, with dreams of sugar-euros in his head, but It is a lot more of a sure thing than adding lead to lighten a professional action up. After all, you get to play the action in the donor grand, before you scrap it out.