To me the limited slots per encounter vs short rest recovery of them is a key element of warlocks so i would be hesitant to change that.
The biggest thing for warlocks is the question of what do you want to be - esp for tome - since their limited known and limited casts drive focus over swiss army knife.
One thing i would say is that while save dying and guidance seem obvious choices, they are also obvious for clerics so if you have a pc cleric, using your bonus cabtrips for other things seems wiser choice.
But i would push to not be the backup mage or an alternate mage but a strong force within a given field... One you can support with invocations.
Focus on illusions, deception and control can play out well and let the mage focus his prepares on others.
As a gm tho the regenerate slots rule you propose would not be one i would be looking for.
The biggest thing for warlocks is the question of what do you want to be - esp for tome - since their limited known and limited casts drive focus over swiss army knife.
One thing i would say is that while save dying and guidance seem obvious choices, they are also obvious for clerics so if you have a pc cleric, using your bonus cabtrips for other things seems wiser choice.
But i would push to not be the backup mage or an alternate mage but a strong force within a given field... One you can support with invocations.
Focus on illusions, deception and control can play out well and let the mage focus his prepares on others.
As a gm tho the regenerate slots rule you propose would not be one i would be looking for.