MostlyHarmless42
Adventurer
A lot of good suggested here. The simplest solution is to perhaps just swap out the current beastmaster rules or use the last revised ranger version and just give them relevant abilities at equivalent druid levels. They arent that far off in levels that it would totally unbalance things. I dont think the druid needs any bonus spells from the archetype as it really does have all the animal stuff on their spell list already.
Giving the share spells option to replace or add to a higher level ranger ability would be somethi g yo consider as well. Somewhere between 8th level and 15th level is probably the range you'd consider for it, either 10th ot 14th is probably most appropriate, albeit it I could possibly see it at 5th level if needed to replace some sort of "multi/extra attack feature if needed".
Giving the share spells option to replace or add to a higher level ranger ability would be somethi g yo consider as well. Somewhere between 8th level and 15th level is probably the range you'd consider for it, either 10th ot 14th is probably most appropriate, albeit it I could possibly see it at 5th level if needed to replace some sort of "multi/extra attack feature if needed".