Yea, for us, the corner also has man coverage on the TE-if he releases, but his run fit is still inside the end. I tell the corners to read the TE. If he sees the run block, he is free to come inside that boxing end.
I too, have been teaching the tackles to grab grass, but I still feel like the back just cuts it immediately outside that little pile, inside the end. That's why I love when the corner is available.
I get worried when the corner is run off by a split. Even if we only let the corner out so far on the split, I still worry about 1)off tackle, and 2) halfback option against a young corner placed in conflict.
Anyway, regarding your original scenario, if the sole receiver on that side is cracking, 1) we know it's sweep, and 2) the corner should be there waiting for him. If anything I would be worried about the back cutting it up to the off-tackle hole. I know he wants to sweep, but a good back may make a good cut. I would just hope my DT's and LB's can react accordingly.