I played one season of USTA league tennis (zero fun - I quit due to the widespread sandbagging but that belongs in your bad league experiences thread) and exclusively played singles. The team captain was thrilled that I only wanted to play singles (no doubles) as no one else wanted to play singles at all and had to be drafted to take their turns at singles. They also did not particularly want to practice singles, had to be drafted to take turns practicing singles with me, and the practice was not that helpful.
When we would play matches it was clear which opponents were primarily singles players and which were doubles players doing their stint at singles (I would ask the opponents after we played). Unsurprisingly, the singles specialists were invariably better at singles than the doubles players. So, if you can get singles specialists, I think that's a good idea. Just my experience.
Good luck with your team!