I think we should create a fork aiming to become a replacement... 

keeping both split functions is quite confusing and will lead to many weird bugs with strange combinaison of usages.

to keep both, we would need to have a global option to choose your favorite mode, or extract both modes into some sort of plugins. This is adding lots of work for not very good benefit, IMO.

From a discussion I had on bugs.kde.org, they cannot chance the split feature in 4.x series, as it is the expected behavioir... so, we would need to advocate for it for 5.0
having an implementation ready, would be a strong argument for us.

if the main dev refuse, we will need to maintain our fork, and eventually users will decide.

so, I'd like to entirely replace the current Split features and keep maintaining this fork as if it would become Konsole 5.0

I actually spent several hours the other night and I got it to a point where I'm satisfied for daily usage.
I will open a Pull request for you to review.