Here's an idea on how to handle things quite differently in D&D5E:
HW Characters deciding to follow their cultural limitations with regard to equipment get the following advantages:
- 1) Once per long rest, the character gains a point of inspiration if adhering to their cultural limitations
- 2) Characters with a proficiency in heavy armor gain a +2 to AC while unarmored or wearing any light armor allowed by their culture.
- 3) The characters may ignore all penalties for having items of inferior materials (See below).
- A character may atone for violating a cultural taboo. The DM may allow the player to spend down-time activity on atonement, or may require the PC to go one session without the Cultural Pride advantage while strictly adhering to his cultural restrictions.
- Characters wielding weapons of inferior materials against superior armor suffer a disadvantage. For instance a character wielding a bronze axe against a steel plate mail or a character wielding a stone spear against bronze armor.
- Characters wielding superior weapons against inferior material armor/shields gain advantage.
- The Cultural Pride ability (see above) allows characters to ignore the effects above while within the Hollow World due to the Spell of Preservation.
A character from the Outer World or a HW character from a different culture may chose to adopt the local culture and gain the Cultural Pride Ability of that culture. The DM must decide how long this takes and may design trials and adventures required for the locals to accept the newcomer as their own. PCs who have abandoned their old ways and seek to return to their original culture may also go under such cultures, but the DM should make things even more difficult for a character who has abandoned his old ways for a long time and not made any attempt to atone.