...and limit to about 1000 thousand blocks (or whatever the 100,000bytes limit is)?
I will just move all the blocks to another address. Still it will be repetitive, but it will only be couple of times...
I am not sure how exactly sendfrom works... Hopefully this will do the trick.
I don't recommend sendfrom.
Better use coin control UI to see what is selected before you trigger the payment.
I'd make mergers of 500 blocks each.
PS: AutoHotKey is really really easy (only problem: it's windows only). You just have to install it and create a test.ahk, then edit the file (right key), paste my code and then run the file (also right key).
But be careful to have coin control UI open and the focus on the first checkbox you want to start with.
If you aren't sure, just open an empty textfile and see what the macro does before you use it.