Hey Jiujitsu, welcome to classicbroncos!
That's not a bad way to look at it especially if you have other things to fix first, to get it running reliably.
But if fixing your tanks is on that list, then the single larger tank is usually more gas than both the others combined, and gets you all new clean stuff as well.
Even though my preference is to run both the new larger rear main tank and the old aux tank together, I'm pretty sure that most people do get rid of the second tank in favor of just one big one. It seems to be the majority of stories here on the forum.
I just happen to like having as much gas on board as possible.
One main reason for the single tank option I think is the proliferation of EFI setups and the difficulty of setting up the shallow front tank with an in-tank EFI pump. The new rear tanks are dialed in for that pretty well, but nobody makes an aux tank pre-made for an in-tank pump.
If you're running an external pump then this is not an issue. But more and more are opting for in-tank models. I'm sure there are kits now that might be used to retrofit an aux tank, but I don't remember hearing of any installs.
The most common setup for those that do retain their front tanks, is to run a separate external low pressure transfer pump to "self re-fill" the main tank when it gets low. Lots of those setups out there working just fine too.
So it just becomes a question of which way you prefer to roll. If nothing is wrong with your current setup, then retaining the old front tank to transfer from is a great way to gain another 7 or so gallons. If you just prefer the simplicity of one single tank and no additional plumbing, then the good news is that just the one 23 gallon tank is still more capacity than you had before.
Fun decision. Kind of the Bronco's stock in trade. Lots of decisions...
Paul