You already can leve link gathering leves. Problem is only the person hitting the node gets the SP so you average the same SP assuming you both do equal work.
I am strongly against making gathering and crafting classes as easy to rank up as battle classes. The only way I'd accept equality is if you nerfed the SP rate on battle classes and no one wants that. No one wants everyone to be maxing all the gathering and crafting classes either. Craft SP is fine. Gathering SP needs small adjustments (add grade 6 and SP on fatigue fail).
Most importantly, people need to stop wanting everything handed to them for free. It seems we have a mix of WoW kids who want to max a class within a week and then those of us who played XI back when it was difficult and want goals to aim for that take time. Hopefully rank 50-60 will take as much SP as 1-50 and 60-70 take as much SP as 1-60. 1-50 is way too fast for battle classes.