No. Part 90 is not your party line.
90.403(a), (d), and (e) all limit your communications to only the permitted uses in 90.405, and ( will hold the licensee responsible for any violations, regardless of who is transmitting under the Part 90 license.
90.405(a)(2) limits your communications to transmissions directly related and necessary to your Part 90 eligibility. Unnecessary communications clog up the limited frequency pool for other eligible Part 90 licensees; they too are paying for a license, and interfering with their essential communications with your non-essential communications can warrant FCC investigation.
90.427(a) makes it extremely unwise to publish your operating frequency and access codes to the public, as you become responsible for a stranger's operation. 90.433© also makes you responsible for their radios, and 90.443( expects you to have some sort of Part 90 compliance information for each radio used, in addition to records of all maintenance. If you're not in direct control of the radios used on your license, station inspection (which you're making yourself an easy target for) will get messy.
If you're claiming eligibility with some purpose you stretched the truth to make, most of your communications won't be necessary and incidental to the operations stated in your eligibility, violating 90.403. If you make up a purpose you have no intention of fulfilling, you're lying on an official form submitted to the federal government and committing a crime; furthermore, you will not be making essential communications as the eligibility does not exist and no essential communications can be made, further violating 90.403.
If you're going to get a commercial license because you are performing commercial activities, go right ahead. That does not authorize you to use a Part 90 authorization to do your Part 95 activities. That is what Part 97 is for. I won't condone the recommendation of Part 90 when the stated purpose of operation is in conflict with the FCC rules and better fulfilled by other services.
All true - there are risks with everything. If one does use Part 90, they just need to be prepared to justify their rule interpretation with the Commission.
Each year there is less FCC enforcement staff, less enforcement, and the trend is to only spend time on incidents that affect public safety systems (considering just Part 90). They are not seeking these things out, and normally do not currently respond for Part 90 business issues even if there is a formal complaint. A good part of NXDN and DMR communications are encrypted anyway (its included free with the digital radio now and enabled with a checkbox...), so there is no way for the FCC to know the message content - its virtually unenforceable. But could they drop in and listen to your radio's speaker - of course. Likelihood? Low.
The activity needs to be a gross violation with limited grey area for a violation these days. Of course there is no grey area with §90.35's eligibility requirement of "....operation of a commercial activity..."
Personally, I have yet to see an NOV for a Part 90 business eligibility issue, but I could have missed it.
Not condoning this, just describing my observations over the years.