User blog comment:PurpleWii/What if more items were like Sterak's Gage?/@comment-26378838-20160418131253/@comment-26378838-20160418162840

1) Champions had changes to their mana regen in 4.20 when the conversion was done, but they were done to flatten the stat progression through the levels, which is the opposite of what you suggest. If Riot would keep that pattern, would be almost double of what it is at early game and that alone would require a gargantuan overall of the game.

2) Considering your suggestion, would require 10% base health and  30% base health, which would mean the latter had to be reworked to ditch the  from its recipe in favor of another  to keep it consistent. Other health items would also need to be nerfed to keep in line and that could lead to health being (perceived as) inferior to other defensive stats.

3) I think considering level 1 stats is poignant because exceptions must be considered. Buying a at spawn as  is valid tactic, but getting 58.25 health instead of 150 is a 61.1(6)% net loss that is only compensated at level 13; in comparison, a  on him went from giving 5 health regen to 3.6, a 28% net loss compensated at level 5. To mirror this, he'd need 809 health at level 1 and an health growth of +172, which would toxic with his kit.
 * And even if we aren't taking into account, Doran items and  also give health and would be reworked too; the latter would probably give 5% health basing on the nature of your proposal, meaning a support  would only receive 27 health from it at spawn, which is laughably low.

4) Your second thought on  makes sense, since purely adding his souls to his base armor reeks of spaghetti code shenanigans waiting to happen. And yes,  should get the same treatment.