We've been discussing this earlier and the plan was to make the split threshold not fixed but depended on wallet size. That way the more you own the higher this threshold. So every coin you gain will improve the minimum size of your blocks and thus improve your staking performance.
It would motivate to hold and buy in stead of sell and leave and it would eliminate the need for manual recombination at the same time. More people, especially the one's who control the big wallets would probably be the one's finding themselves without a need for manual recombination and let their wallet just stake 24*7 securing the network even better that way.
How exactly this will be done and tuned is still open for discussion as far as I know.
I've have some idea's for whenever we have to decide what it's going to be, but for now that not too relevant I think.
Correct. Right now it will allow you to set the split/combine threshold using startup/config switches. Default is split nothing below 5 and combine if possible up to 20. It can be set to a max of splitthreshold of 10 and combine of 40.
I will allow these to increase for future, but based on wallet size and once the hard fork takes effect.