D&D General Making consistent Monsters?

[Scurvy_Platypus]

I think LevelUp is going to be the most help here. That said, 5E is not a point buy system. You are going to have to wing it a lot.

Yeah. Like I said, I'm willing to do the work but it'd be a lot easier if 5e had some point-buy options. I'm aware of Anime5e existing but won't touch it for a variety of reasons. Maybe I'll just have to figure out something myself; however, that still requires an underlying base, so that if I muck it up, at least it'll be consistent. Sounds like I'm going to have to look closer at LevelUp.

 

[J-H]

While I'll look at LevelUp and MM on a business card... if I wanna grab a critter from Palladium Fantasy and build it for 5e... which is gonna be "better" (more complete) for doing so? I need to be able to figure out how to "price" funky abilities, as well as creating the basic chassis that those abilities are gonna be attached to. Yes, I get that I can "look for a similar ability on a 5e critter" but part of getting inspiration and converting critters is grabbing something that's "unknown" in the 5e rules and surprising folks with it.

MM on a business card has a quick comparison chart for 6 numbers that'll get you pretty reliably close every time. Stat out what you think a monster should be, and then check the chart to see what CRs its AC, HP, to-hit, damage, and best save line up with. Take the average value and that puts you in about the right place.
The only funky part is that monster Proficiency Bonus is linked to CR, so if you bump something from CR 10 down to CR 8 you should take 1 off its to-hit and proficient skills/saves if you want to "follow the rules." Realistically a +1 doesn't matter... you can always override it by just mentally giving something a trait like "Has the Poo-flinging fighting style for +2 to hit with poo" to put your numbers where you think they need to be.

Then the dice will cheat you anyway. I put 4 slingers with +7 to hit for 1d4+3 against a level 7 party tonight. They got off 12 total attacks (including 6 with advantage from surprise & at a barbarian) and only hit once against ACs of 15, 16, 19, and 22. :-(

The problem isn't so much "what to use" but more "is this gonna kill my group outright or just singe their eyebrows and make 'em panic?" And that's what I need some sort of underlying base to build my critters from and hopefully have an idea of whether my grizzly needs a bear-hug attack or just flies around zotting everyone with its lasers.

Yep, eyeballing the CR with Blog of Holding method should be fine. As long as you're pretty close you are fine.
Also keep in mind that 5e characters are very resilient and hard to kill unless you are really overwhelming them.