New DM on House Rules, concerning Nat20 & Rule of Cool

As a DM making a house rule, am I allowed to grant "Rule of Cool" to Natural 20 rolls in exchange of giving "Rule of Uncool" effects for Natural One rolls? (but all within the boundaries of RAW as well).

  • In battle, a small PC rolling Nat20 successfully maneuvers himself and climb on the back of the big bad creature (Legolas Style), only to roll Natural 1 in his attack and accidentally hit his allies.

  • Failing Deception on guard with Nat1 roll additional 2 arrives and a High Ranking Knight, only to roll Nat20 and convinced the High Ranking Knight instead literally allowing you to pass the area with no consequence at all.

I just want to encourage imagination by introducing some Matrix dodges and Epic fails in the game that is somewhat lighthearted and funny especially to noobs like me.

Am I being a bad example of being a DM? Should I discontinue this approach?