Potentially you can swap all the Omnipod supplies (including insulin) to Aetna, but unless you are on Medicare you face the very real possibility of Aetna and United Healtcare having two different set of rules which mean neither of them are responsible for anything.
In any case, this is the first time I've heard of anyone managing to get any company accept that DME supplies are DME supplies ;-)
Incidentally, I'm currently paying $30/30 days for test strips (300) on prescription. The price Walmart is charging for these is $467 (i.e. $78 for 50), so even though my DME coinsurance is (IRC) 10% - $46.70 - I'm still ahead on the prescriptions; $16.70 a month to spend on those candy bars. Since this is an obamacare plan it doesn't make any difference to me whether I pay a "co-pay" or a "co-insurance" and since I won't max out I'm better off with the $30 "co-pay".
There is no choice but to ask all the questions and do all the math.