D&D5/System

=Rule changes=

Warlock Spell Slots
Warlocks may cast an infinite number of spells of the same type by using a spell slot.

Training
Each level, characters gain a proficiency point, usable to buy a skill, Expertise in a skill, a tool proficiency, or a language proficiency. Rogues may now also buy Expertise a second time, including with their class ability.

=Unearthed Arcana=

Proficiency Bonus
1  +2 2   +3 3   +3 4   +4 5   +4 6   +5 7   +5 8   +6 9   +6 10  +7 11  +7 12  +8 13  +8 14  +9 15  +9 16  +10 17  +10 18  +11 19  +11 20  +12

Warlock
A Spell slot regenerates in 1 minute? (roll d10 each round, if the number is equal to or lower than the number of rounds since casting the spell in the spell slot, the spell refreshes and is ready to cast). An action / bonus action could be used to refresh all spells / one spell (feat?).

Concentration
One concentration spell each level?