To those that have completed the thieves guild questline, can it be done without investing in sneak or pickpocket?

It could be a challenge. Sounds fun, I might try that.

according to http://www.rarityguide.com/articles/articles/1015/1/Skyrim-Walkthrough-Thieves-Guild---A-Chance-Arrangement/Page1.html you can do the first quest there without sneak since it completes even if you get arrested

second quest also doesnt need sneak since there are alternate ways of doing it

I havent completed the wholse storyline but am guessing its possible, though prolly a bit harder

Yes, at the time when I had very little sneak skill, I still completed the whole questline with ease. We're talking like, 15-25 on sneak skill.

Cool, I plan to make some alchemy potions to fortify sneak/lockpick/pickpocket if needed too, so its good to know with low skill its possible.