The thought occurred to me that many people don't like seeing their character being laid low immediately after starting a campaign. So why not boost HP at the start I thought... to at least Level 3 worth (without the being Level 3) but I'm not a fan of preferential treatment, it would need to be a change across the board PCs, NPCs and Monsters alike.
While I agree that Class should be the primary factor when calculating HP as you progress, but I like the idea of Race providing variation e.g. Yes you're a Wizard but also a Goliath (Racial Trait +1 Con, so increases Race Hit Die by one step) and a medium sized creature...
So your starting Hit Points look like; HP= 1d6(Wizard) + 1d10 (Goliath) + 1d8 (Medium) + Con Mod
1d8 would be the baseline for Racial HP, your standard Human analogue.
A drastic difference for low level play and monsters (hardier goblins for instance), but said difference will have very little effect later on, HP increases per level are still the same. Would this be relatively balanced?
Frankly, we like low HP at low levels, the game has enough HP bloat as it is...
What is the challenge if you have enough HP for tier 1 that things aren't quite the challenge they could be?
BUT... since you
want to go this route, there is nothing wrong with it. It is better than 3x hp at level 1 or whatever because it is no longer just
class that helps your hp.
I would
NOT recommend it as a change across the board, however, but let's look at my favorite test subject: the commoner.
HP = 1d??? (no class?) + 1d8 (human default) + 4 (medium) + 0 (Con mod). So, 8 or so on average?
Perhaps use the sidekick classes (expert as default, so d8 for medium creature) would add a bit more, making it 12 or 13 for a commoner as a level 1 expert?
In general, I think it would be easier to simply grant all creatures two addition HD (one for class, one for race?) with appropriate CON bonus because I think that is what you will often get.
So, your aforementioned goblin would become 4d6 with 14 hp default. (100% increase)
A mastiff would go from 1d8+1 to 3d8+3, increasing to 15 hp. (200% increase, making them useful...)
Yet something like a Wyvern would go from 13d10+39 to 15d10+45, from 110 to 127 (15% increase or so)
Etc.