Hi OP,
I can help you on this topic. I am a budget traveler myself and I primarily focus on redeeming Hilton points on mid to low end properties (Hampton, HGI, DT, Hilton) in regions of my interest. It is true that in most cases redeeming Hilton points on lower end hotels are not worthwhile, in edge cases (or as you call it, "unicorn") it can still offer fantastic values. What I've noticed is that, while most Hilton properties have dynamic pricing (and the cpp is not good), a handful of them still have one flat award price throughout the year. And of course you should always consider stacking 5th night free.

Here are my top two picks in Europe:
Croatia: Hilton Garden Inn Zagreb Radnicka (20,000 year-round)
Austria: Hilton Garden Inn Wiener Neustadt (20,000 year-round)

These are both very new, and best of all, they are not far from each other, so you can burn 80k on a five-day stay for each property in one long vacation. Rest assured you can find enough sightseeing and activities in both regions, especially if you rent car. I've personally stayed at the HGI in Zagreb (5 days) and I loved it.

Germany: Hampton by Hilton Dortmund Phoenix See (20,000 year-round) - I don't know enough about western Germany but the cash rate there (>100 EUR) also makes this a good redemption.

Some other HGI hotels with good values during peak season (e.g. summer) where cash price is high. During winter and low seasons it's better to pay cash than redeem points.
Romania: Hilton Garden Inn Bucharest Old Town (25,000 year-round)
Romania: Hilton Garden Inn Bucharest Airport (20,000 year-round)
Lithuania: Hilton Garden Inn Vilnius City Centre (20,000 year-round)

Some properties to consider beyond Europe:
Turkey: DoubleTree by Hilton Afyonkarahisar (15,000 year-round)
Turkey: DoubleTree by Hilton Hotel Avanos - Cappadocia (15,000 year-round)
Turkey: DoubleTree by Hilton Adana (20,000 year-round)
Turkey: DoubleTree by Hilton Van (10,000 year-round)
Turkey: Hilton Garden Inn Safranbolu (10,000 year-round)
Turkey: Hampton by Hilton Antalya Airport (14,000+; dynamic pricing but cpp is ~ 0.5)
Oman: DoubleTree by Hilton Muscat Qurum (20,000 year-round)
Egypt: Hilton Luxor (30,000 year-round; worth it during winter high season)

I hope this helps The silver lining in Hilton's dynamic pricing and across-the-world points inflation is that, you only need to find a few unicorn properties (such as the above), stay 5 nights, and burn all your points, and you don't have to worry much afterwards.