I think the updated Core PH should have the spells necessary to fulfill the existing class/subclass fantasies. There are a lot of melee spellcasters, so there should be a decent variety of such spells to enable those builds. Here are what I feel are good parameters:
- If a previously printed non-PH spell is popular in theme and needs an update to clean it up, they might as well include the updated version in the PH. Does Booming Blade, Greenflame Blade, or Lightning Lure need a power shift, or a description or template update to make it work with any other game updates?
- If the previously printed spell is popular and does not need an update, leave it in the sourcebook it came from.
- After deciding the results of previously printed spells, create brand new spells that help fulfill that weapon spellcaster theme/fantasy. They should be unique from everything that came before, via damage type and/or any special rider that accompanies the damage. Examples below:
- Greenflame blade has fire covered, Booming Blade covers thunder, Lighting Lure covers lightning, and True Strike covers Radiant, so try to focus on the other damage types.
- Don't reskin a "Booming Blade" variant as having piercing thorns that hinder and harm the enemy, because Ensnaring Strike already has that theme covered.
- Suggestion: Bleeding Blow: A Necromancy (necrotic) spell that causes your weapon to deal extra bleeding (necrotic) damage.
- Suggestion: Dispelling Strike: An Abjuration (psychic) spell that lets you attack as a Reaction when someone within 10ft. reach of you, that you can see, casts a spell. If you hit, it forces a Concentration check at disadvantage or the spell being cast is lost and concentration on an existing spell is disrupted.
- Suggestion: That anime weapon attack, where the weapon is swung, causing a 30 ft. (force) wave in a line. Deal extra damage to the first person in the line, and normal damage to everyone behind them.
Stuff like that.