At least, I will treat the example whose classical part is finite dimensional and their tangent complexes have finite cohomology at each point.
(Edit: I am also considering fixing constructions of derived quot schemes by them because that constructions are failed according to this paper)
Edit(5/9): In the above case, I especially interested in when both $L_1$ and $G$ are infinite dimensional.
Then, we may be able to replace the structure dg-sheaves $\mathcal{O}^{\bullet}_{[L_1/G]}$ with $Sym_{\mathcal{O}_{[L_1/G]}}(Q^{'-i})$ with each $Q^{'-i}$ finite rank if we consider replacing the corresponding bundles on $L_1$.
However, I have no idea how can $[L_1/G]$ be replaced with a finite dimensional model (for example, $[L'_1/G']$ with $L'_1,G'$ finite dimensional).
Edit(5/7): In this paper, dg-stacks of logarithmic flat connections is treated. By using bundles of curved dgla, the dg-moduli stack is constructed. But, it is infinite type (in detail, the gauge group is infinite dimensional). The author construct a replacement which is a finite dimensional model.
His approach seems to depend on the subject he is dealing with.
Can we make such replacements in more general situations ?