Both of those seem fairly reasonable to me as a mostly heal/ranged player who mostly dabbles in NIN from time to time. There is obviously the slidecasting element to that so I'm not entirely sure how caster uptime could be constrained but equally I'm not that creative. I suppose it would be reasonable to have some add phase or something where ranged (preferably casters) have to do something to facilitate melee uptime? Mostly the having ranged/casters doing something since I still prefer melee uptime being tied to the melee player's skill rather than dependant on someone else (tank not withstanding since positioning should be their job) doing their job properly. I'm sure people better at melee and the game in general than me will have better ideas.