Question: Let $\varepsilon>0$ and $N\in\omega$ be sufficiently large (depending on $\varepsilon$). Let $h:\subseteq N\rightarrow N$ be such that $h(B)\notin B$ for all $B\subsetneq N$. Must there be $B_0\subsetneq B_1\subseteq N$ such that $|B_1|\leq \varepsilon N$ and $h(B_0)=h(B_1)$?
More generally,
Let $a\in\omega,\varepsilon>0$ and $N\in\omega$ be sufficiently large (depending on $a,\varepsilon$). Let $h:\subseteq N\rightarrow N$ be such that $h(B)\notin B$ for all $B\subsetneq N$. Must there be $B_0\subsetneq B_1\subsetneq\cdots\subsetneq B_{a-1}\subseteq N$ such that $|B_{a-1}|\leq \varepsilon N$ and $h(B_0)=\cdots= h(B_{a-1})$?