Joining new employer while on unpaid leave with current employer during H1B transfer

[expertjam]

I wanted to request guidance regarding my immigration situation. I appreciate your thoughts and guidance.

I am currently working with an employer A on H1B and, in parallel, waiting for my h1b transfer to be approved for employer B(transfer application is pending for almost 6 months).

1. Is it legal for me to take unpaid leave(FMLA or LOA) from employer A and join employer B on h1b transfer receipt? Once my H1B transfer is approved, I plan to come back for a day and resign from employer A. Will this be in violation for H1B policy?

2. Employer B wants me to join asap (preferably within a week of h1b transfer approval). However, I would not like to resign from employer A until March 22nd, annual bonus payout day (employer A). In a hypothetical scenario, if my h1b transfer is approved by Feb 25, can I just take unpaid leave from employer A on Feb 26 and join employer B so that I can come back on March 22nd and resign from Employer A (and collect my bonus)? Do you anticipate any legal challenges with this approach?

Thanks a lot for your help.

Akhil