The new assignee will be held to the same standad as the original and remedies are retroactive. Meaning if the performance is substandard the law will allow a default and remedies under the law or contract. Whta you are worried about is is anticiptory breach and that means you think there will be a breach and you are entitled to assurances that the assignee can perform before you allow the assignment.
The assignment will be controlled by the contract, not by statute.
If the issue is whether the Assignee can meet the requirements of the lease and the Lessor is concerned about whether the approval is being withheld or give under a "reasonable" standard, the financial stability and ability can be questioned. If it can be seen that the Assignee is not financially stable, then withholding consent would not be unreasonable.
This answer does not constitute legal advice and does not and is not intended to create an attorney-client relationship. The law may vary depending on the state in which you reside. It is intended only to give some direction in which to seek assistance