I'm not sure if my advice is worth very much, having been up for 4 hours last night and 5 the night before! However, I feel your pain and didn't want to just ignore your plea. I think that if the NWs are because of OT then you are probably right to try to let your lo catch up during the day up to a point. With dd1, who is a very good sleeper so we haven't had to do this often, we tended to set a time that we didn't want her sleeping past but let her sleep until then. For example, now she is 2 and sleeps 2 hours during the day (12.30 till 2.30) - if she is really tired we let her sleep, but make sure that she is up by 3 so that it doesn't affect going down in the evening.
Are you able to put her down earlier than her usual nap times? That way she can get an extra 15 mins or so, but still be up at the same time and keep the routine a bit better.
My experience with dd1 suggests that when I let her sleep too much during the day, the problem becomes settling her at night rather than her NW - don't know if that is just her or whether this is the way they all react.
HTH. Cx