Hi Gabriel,
It depends.
Will your solution interact with SuccessFactors using any APIs? If so, you'll need to adapt these to on-prem APIs.
Using UI5 as your presentation layer _should_ make the solution seem familiar for both SuccessFactors users and OnPrem, but as currently there is very little of SuccessFactors using UI5, so you may be tweeking it quite a bit, and you might want to un-tweek for the onPrem audience.
Good luck, would love to know a little more detail around what you are thinking of building.
Chris