I'm not that up with Ilford's developers and what they actually contain, but it does appear that you could be onto something regarding just adding some Potassium bromide.
A quick glance at Ilford ID-62 developer and Ilford ID-78 developer shows that they are almost identical with one notable exception. No. 62 has 2g P/Bromide, whilst No. 78 has 4.5g P/Bromide.
That isn't really all of the differences, but mainly the major difference.
Effectively both of those developers use almost the same ingredients, but in differing amounts.
Could be worth a try, you would have nothing to lose as you are talking paper, not film.
Getting chemicals isn't that easy, but it's doable. Vanbar in Melbourne would be pretty much the last bastion of raw photographic chemistry in the country.
I have almost enough chemicals to last at least 10 years at my current rate of usage, but with retirement looming, I'm not so sure.