I think Eriksen plays MUCH further forward than Modric and as such, isn't suited to a central two, unless we're at home against a lower league team and can afford all out attack.
Even simple stats would show they play different roles. Eriksen is about goals and assists. Modric was the assist of the assist. Different animals.
Actually, he's a bit broader skilled than that, he doesn't have many assist so far, but he's average over 2 key passes a game, and if you look deeper at his role, it's pretty clear he's the most important person for us in attack:
http://statsbomb.com/2014/10/attacking-contribution-metric-and-man-uniteds-reliance-on-di-maria/
The article is now a couple of months old, but I doubt his influence has really diminished.
He's also throwing in a couple of tackles, an interception and a blocked pass per game on the defensive side on average, and his distance covered against Everton for example, was only about 300 metres less than Kane's monster 13km effort.
He's not a DM, but he's a lot more involved in the press now than he was a month and a half ago, and we don't really notice it.
I don't know if he will ever be really a Modric-type player, as he comes forward more and likes to score. But he did drop deep against Hull and run the show, so it's in him if you ask for it.
That said, Eriksen isn't Modric, and Pochettino isn't Redknapp. We may find that we'll be in a different place that works fine on its own.