I would do things differently in 2 main aspects, what reprints I would choose and how I would design new cards.
Wizards has already been trending towards this, but I wouldn't really reprint specific big money cards, instead focusing on multiple $2-5 cards. I much prefer this because it's harder to for scalpers to sell a bunch of $3 cards than it is to sell a single $30 card (which decreases the likelihood a certain precon's price will be inflated). Also, it helps keep the price of solid background cards like
Lightning Greaves,
Blasphemous Act,
Rapid Hybridization, etc. cheap and available. I personally don't think the goal of precons should be to reprint very expensive cards. They should be more for creating solid, affordable decks for new players to get into the game with or established players a deck to have a bit of fun with.
In terms of new cards, I would put less of an emphasis on creating generically good new cards. I want cool, specific cards that shine only in certain strategies. The cycle of free cards in c20 (ex.
Fierce Guardianship) is the perfect example of generically good cards I don't want to see in preconstructed products. All of the members of the cycle except of
Obscuring Haze are good in pretty much any deck that could run them. On the flipside, I love the new cards in the Witherbloom Witchcraft precon this year.
Ezzaroot Channeler,
Trudge Garden, and
Blossoming Bogbeast are really only playable in lifegain decks, but they're
really good in lifegain decks. Additionally, I would try for new design space. C21 is really good for this (imo), but C20 was just plain uninspiring.
Kathril, Aspect Warper feels very similar to earlier commanders,
Jirina Kudro is just a generic token maker + buff on a stick, etc.
TL;DR I want the precons to be less about reprint value & powerful cards, more about being interesting and a fun addition to the format.