Yes your X>A>B and X>C>D would both work at the same time since the A>B and C>D links would keep the mobs non-grey to a good chain at all times. The downside I see to this is if you want to level multiple teams. Your X,A,C accounts would be the only ones getting free levels. The normal chain would get you 4 (X,A,B, and C) accounts getting levels from a 5box team.

The chain also will change how many granted levels your main account would get per 5box 60 team. The normal chain gets 55 levels for the main account where your double chain would get 90. The difference is the total amount of granted levels across all your accounts. A normal chain gets 55+52+45+30 = 182 levels across all accounts per 5box 60 team. Your double chain would get 90 for you main, A&C would get 30 each, and B&D would get 0 for 90+60 = 150 total levels.

So it really boils down to if you want more help creating more teams, or if you want more free levels on your main account. You are however boxing, so I would assume having more characters of different classes available would be a good thing, suggest going with the normal chain.