Can I let a single PC use the Spell Points variant rule without unbalance?

One of my players (level 5 Druid) has been looking at the Spell Points variant rule in the 5th edition DMG (page 288) and wants to use it for his character. I’ve talked to the other players with spellcasting (a Wizard and an Arcane Trickster) and they would prefer to stick with spell slot. So,

  1. Would there be any problem in letting the Druid use Spell Points while the other PCs used spell slots?
  2. Would anyone be at a disadvantage by doing so (druid or other PCs)?