In the Magic: The Gathering Pioneer format, a Mono Blue deck offers a range of innovative build options. The usual archetype contender in the metagame is the Mono Blue Spirits, which is a quiet tempo-ish aggro deck that utilizes cheap card draw, and counterspells.

Here are a few ideas for some innovative Mono Blue builds:

1. Mono Blue Devotion Combo:
   Combine cards like Thassa, Deep-Dwelling, and Agent of Treachery for a flicker-based control/combo deck that exploits powerful enter-the-battlefield triggers.
2. Mono Blue Tempo Flyers:
   Create a deck focused on aggressive flying creatures like Siren Stormtamer, Brazen Borrower, and Tempest Djinn, backed by disruption spells to control the game’s tempo. This build was aligned with the Devotion to Blue strategy back in its Standard days.
3. Mono Blue Artifacts:
   Craft a deck that capitalizes on artifacts synergies with cards like Emry, Lurker of the Loch, Gadwick, the Wizened, and artifacts that provide utility and card advantage.
4. Mono Blue Mill Control:
   Explore a control-oriented build that utilizes mill cards like Sphinx’s Tutelage, combined with counterspells and card draw, to disrupt opponents’ strategies while milling their decks. There are also Dimir versions of this deck archetype.
5. Mono Blue Planeswalkers: (or splashing White)
   Construct a deck featuring planeswalkers like Teferi, Time Raveler and Narset, Parter of Veils for their control and card advantage capabilities, along with protection for your strategy.
6. Mono Blue Wizards Tribal:
   Develop a tribal-focused deck that utilizes wizards like Siren Stormtamer, Gadwick, the Wizened, and Wizard’s Retort to create a synergistic and interactive playstyle.
7. Mono Blue Morph Surprise:
   Build a deck around morph creatures like Thousand Winds, and Stratus Dancer, keeping your opponents guessing about the face-down creatures’ potential, and do some board advantage effects as you face them up.
8. Mono Blue Self-Bounce:
   Create a deck centered on returning your creatures to your hand for additional value with cards like Quickling, Shaper Parasite, and Aether Adept.
9. Mono Blue Clones and Copies:
   Innovate a deck focused on cloning and copying spells and creatures, using cards like Clever Impersonator, Vizier of Many Faces, and Quasiduplicate.

Remember that the effectiveness of these innovative builds can depend on the metagame and your playstyle. Experiment, tweak, and adapt these ideas to suit your preferences and the dynamics of the Pioneer format.