The glaring issue with this mechanic is that as it would appear on multiple cards that could lack the exile-clause invoke would become more powerful/problematic.

If you were to create and use that keyword the central question would be whether it's not a better idea to generally exile the cards from the graveyard, delve-style.

Also delve-style there is a question of whether this should be able to pay for colored cost at all, too.

As an individual card design this seems fine.

I figure that cards that just have invoke rather than grant invoke wouldn't need the exile clause for power concerns. It's also only creature cards compared to all cards, which is a huge nerf over delve (which tended to get juiced by fetch lands)

The main reason for the exile clause though is that the joke is that people often turn cards in their graveyard sideways to indicate that they're exiled instead