Crazy Kids' Clothing sizing

Okay, I'm just about up to "here" with the sizing on kids' clothing. C started out "normal"--when she was 3 months old, she outgrew the 0-3 clothes, when she was 6 months, she outgrew the 3-6 months clothes. However, she kept wearing 6-9 months clothes until she was 12 months, and wore the 12 months clothes until she was 21 months old. I know that's all because she's small, but now we've reached the ridiculous point. At 21 months, she started wearing 18 months shirts, and stayed in 12 month pants! She's still in mostly 18 month shirts (dresses and jumpers) and can wear some 24 month ones, if they're on the small side. Pants, on the other hand--12 month pants are now too short, but 18 month pants are sometimes the right length, but too big in the waist and fall off (I tried taking them in with the sewing machine, but they're not too big enough to have enough extra fabric to use)! BUT, I put her in 24 month/2T crops the other day, and THEY fit, at crop length and without falling off the waist. How bizarre is that? Dresses, skirts and jumpers are about the only thing I can find that fit the child correctly, but F doesn't want her in skirts all the time (just church, basically). He thinks pants are better for playtime. I feel like pleading with the kids' clothing industry--would somebody out there make a pant that'll fit my skinny kid!?