Hi Antonios
It looks like you have already answered your question for you. Development skills have diversified a lot with SAP in the past few years. Having the front end experience to enter a junior SAP developer role could be quite useful
UI5, Java/javascrip, HTML5, etc are all useful. I recommend you have a search and also look at the open.sap intro courses for Fiori to get a better appreciation.
The other complimentary skill is to look into SAP's UX strategies which the UI techologies work without. SAP's goal of simplification and putting user experience first is forcing a lot of us to consider what we design.
Good luck with your skills development.
Regards
Colleen