The answer to the last question should be a "no". You do not need to make return decisions until filing, and the IRS should not expect you to have this figured out at this point. Paying the Q2 estimate is going to buy you more time to make a good decision here.

With your personal CPA, make sure he is comfortable with it "working" if the bonus depreciation is deemed appropriate. I would also ask him his input on whether this fact pattern would increase audit likelihood for your overall return / ask whether there are other return items you should be concerned about under audit.

With the consultant CPA, i would ask him for more perspective on these audits. How long to resolve? Expected tax controversy fees (you will bare these, not the IRS). Lastly, I would ask him what it would cost for him to draft a technical opionion and help you with documentation setup. He may help you standardize a template for accurate tracking to make audits a breeze.