So both those are reasonable if you read the meta right. I would also say that depending on what budget means (0-proxy vs 5-10 proxy vs infinite proxy) and also how much money is budget for you ($400 vs $1000 vs anything but power/shops/bazaars) makes a big difference in answers to this question.
In general I would tend toward unpowered blue deck over something like red prison in vintage? In a 5-proxy meta I would do this every time (3 mox/lotus 1 time walk 1 ancestral, and the rest of the deck is legacy cards).
Side note: I’m not sure why PO has never looked into 1-2 copies of Ascendency?
I think they just don't need it, and also the critical mass of free spells/cheap +CA spells to trigger it has gone down. When gush and dig were still legal along with 4 probe, there were some versions of the deck that could even hang with the shops deck of the time a bit.
Now, however, what would it be replacing that isn't already doing something better. Plus it pulls you into a 3rd or 4th color depending on the build.
The interaction with painter is way to significant to ignore. It may only see play in 1 deck but may push that deck from relative obscurity to a deck that can steal weekly challenges and league 5-0s.
This card has to be worse than red blasts 1-8 in painter though right? Do you have room for 9+ of that effect? IN all the old build of painter i played i struggled to play more than 4 and even with MM restricted I can't imagine playing more than 6-7.
What specifically is your goal? Do you want to play at EW and do well enough to earn an unpowered prize? Are you just playing locally? Trying to get a local scene started?
I asked because depending on your location, you may be able to play some number of proxies at proxy events. This is very common in the US. If you are trying to build something to do well at EW, for example, your best bets are probably Colorless Eldrazi or Mono Red Prison in terms of historic performance.
Define critical mass? I think there are exactly two that are better or don't also put large (larger?) constraints on your deck than this. Outcome would be the obvious other, but there is a lot of hate for outcome in the format at the moment (karn, ouphe, narset), only some of which similarly affects this card.