Hmm, well, such changes could definitely improve Cleric kits. Making major buffs improve with level would be broken (non-dispellable +13 str/dex/con at lvl 39 ) but minor buffs like +HP and duration scaling tilll high levels might be a good addition. Thank you for that suggestion!
I think that's a mjor improvement, though one could always argue that getting +78HP's from holy power/righteous magic is broken (instead of +40), even though I don't think it is. The major improvement from that would be the duration, as it makes sequencing buffing a lot easier so it's mostly a convenience improvement. Well, the HP's can help a little bit as well.