[2023] What if there were Tier 3 boots?

I don't know what they would do exactly, but I have a few ideas:

• 1) They would cost more gold (duh)
• 2) They would combine from tier 2 boots + something (duh)
• 3) They would count as legendary items so you'd get an extra stack of your mythic passive (nice)
• 4) As to what they DO I'm thinking either they offer an even more pronounced effect of what they already do (for example legendary Ionian boots with even more ability haste and summoner spell haste) OR you could use them to combine the effects of two different tier 2 boots together.

For example: Merc Treads + Swifities = higher speed merc's. Assume all the costs and numbers get balanced out.