The city of Los Angeles has taken an interesting approach to accessory dwelling units (what we generally call laneway or garden suites here in Toronto). In an effort to streamline the approvals process and bolster the supply of housing in the city, they've gone out and pre-approved a series of "standard plans" that you can quickly implement on your property. The idea here is that all of their approved plans have already been checked for compliance with the various building codes. So those reviews don't need to happen before a permit can be issued (though the building department would still need to review any site-specific conditions).
What that means is that if you're in the market for, say, a one-storey, one-bedroom ADU at around 450 sf, you can simply scroll through their list and find the one you like the most. Here is one that fits this criteria by Design, Bitches (I just wanted to mention this firm name). The potential downside of this approach is that it could encourage less architectural experimentation. On the flipside, many of their approved designs are really nice and so maybe it's a boon for those who are lacking in good taste. Either way, if you want to encourage more of something, the way to do that is to reduce friction.
To start to give you a sense of how meaningful this could become, the city of Los Angeles received 1,980 applications for ADU construction back in 2017. This is the year in which the state changed its regulations so that ADUs were no longer prohibited in some municipalities (I don't know all of the specifics truthfully). Last year, LA saw 5,374 applications and I suspect the number will be even higher this year. Should other cities look at pre-approving certain designs? And could this be an approach used for even larger building typologies? Speed is good.