I had typed a long reply but it got lost somehow, possibly my PC lost internet connection while sending, so here is another attempt:
It would be preferable to have both automatic split and automatic merge (and we can discuss if they should default be enabled or disabled)

Automatic split could for example only activate when you send an amount to yourself that is larger than a variable "Max input size"
For example if you select a 15k input and send to yourself a 3k block from it, then you would get a warning: about the splitting of the total input and if you confirm with max input size configured to 4k then you would end up with 1 x3k and 3x 4k blocks automatically.

For automatic merge you would only need to do something similar as Orbitcoin has done, where blocks below a certain size are not split when they stake, although it can be improved to check the *output* block size instead of the input size.
For example, if you have the variable "minimum input size" configured as 1500 and you are staking a 2k block that is earning 400 Hyp, today you would end up with 2 blocks of 1200 and next stake would give you blocks somewhere around 700-800 Hyp and so on. When the automatic merge sees that the output would be split in blocks smaller than the minimum input size, it would only add the stake reward to the input without splitting it.

I hope this description helps and makes it clear what the idea is of the automatic split and merge, let me know if there are questions for clarification.