Maybe add some more ramp (Farseek) or some more stall (Fog)?
Never heard of this card until now. Cool concept and very original.
Also dual/shock lands would be great to add (albeit maybe out of your budget). Hinterland Harbor and Breeding Pool in particular.
Honestly, I know it's not exactly a budget, but you can mill your entire deck and Unburial Rites Angel of Glory's Rise to bring your four biovisionaries back to the battlefield, thus way ending the game at the end step.
It's a novel idea, but I think that most metas are heavy on control elements, and since you need all four of them to work, all it would take is an O-ring or other exile effect or some -1/-1 counters to completely upset your win-con.
It's a very fragile deck. I would consider running lots of blue counterspells.