Ah, I had the Paladin's spells in mind for the campaign that is about to start. He is, however, going to start developing spells at a later level anyway. I looked into a bit into HARP, RM2, RMSS and RMU on the matter of ESF or Spell Roll and then finally decided to stick to the HARP magic system. (Although I still feel it a bit reduced compared to the vast amounts of spells in Rolemaster.) I might, however, change spells like Minor/Major Healing into something more Laying on Hands like ones with a healing per round or minute of concentration. I never really liked the high amount of healing gained from those two spell, actually never liked the "heals d10/10 hits"; too DnD I guess.
Thanks for the comments, hints and ideas.