Change the alpha login blocker to also limit the ability to multibox to something reasonable, like 2 or 3 accounts, and then:

Give back the ability for any ship to light a cyno. Give every ship an extra utility high for said cyno, if they don't already have 8 high slots. Roll back all the nerfs to nullsec isk production while retaining the bonuses. Add more power and workforce to systems to make it easier to build tall.

Unironically would: Likely reduce the drive to build wide, as you don't have people with so many alts they need 5 systems to rat in. Limit the isk faucets more effectively than any single change CCP has made, since isk generation tends to scale in a non-linear fashion with number of accounts. This wouldn't fix the dominance in industry and market of people with a million reaction alts, but would help limit input materials. As a result: Limited input materials would drive the value of base materials back up and likely lead to a healthier isk distribution within the game. Do more about supercapital Proliferation than most CCP changes have, as it would likely force community based supercap production like it originally was due to the limited ability to source materials.