Sure, why not? A toner is a very broad word that can mean all kinds of things. If your goal is to condition you skin after washing, then using a conditioning agent - a cationic quaternary compound like Incroquat BTMS-50 or Ritamulse BTMS-225 or a cationic polymer like honeyquat or polyquat 7 - is a very good idea.
If you use something like BTMS-50, BTMS-25, or BTMS-225, you'll end up with a milky mixture that's more of a lotion-like consistency. If you use one of the cationic polymers, you could have a toner that could be completely clear.
You can use up to 5% honey quat (cool down phase), up to 5% polyquat 7 (heated water phase or cool down phase), up to 2% polyquat 44, and so on. So you'd use your cationic polymer, preservative at the suggested usage rate, and distilled water to make up 100% total. And you'd have a toner for conditioning your skin!
Related posts - toner recipes with cationic polymers:
Experiments in the workshop: Min-maxed toner
Experiments in the workshop: Min-maxed toner becomes becomes a facial gel
Formulating for dry skin: Toners continued...
Making a toner for the oily skin type