I recently rolled a bard for a new game set in a low fantasy world. It's a halfling bard, with 17 CHA and 16 DEX and +0s or +1s elsewhere. In the party there is also a defensively minded Paladin, a gunship rogue with a crossbow, necromantic offensive warlock and a fighter inspired by 4e warlords.
The party lacks a bit in healing and utility spellcasting I would like to fill in that niche while still having a considerable presence in combat. To accomplish that I wanted to embrace a Spellsword approach.
I would like to be able to combine spellcasting (buffs and debuffs, preferably as cantrips or low level spells) with DEX-based combat opportunities. I know that College of Valor has some options, but it seems like a huge waste (I have high Dex and therefore prefer light armor, I will not use non-finessable martial weapons, and Extra Attack doesn't seem to fit well with eventual Battle Magic). I would like to have a "cast and slash" battlefield presence, but if I had opportunities to use my bonus action for added awesome I would consider it gladly.
Is it possible to optimize the character to accomplish those gameplay goals and if yes, how?
I am limited to PHB and I need a very good arguments to be allowed to multiclass. I briefly I mentioned possible MC into a Paladin and had a mixed response.