Not a little funky IMO. Very funky. I don't think I'm in the minority in believing that.
https://www.reddit.com/r/LancerRPG/comments/mactxi/hex_or_grid/
15.5% prefer Grids over Hexes. And I wouldn't be surprised if only 15.5% of that 15.5% range with diagonals as 1:1. So your decision is aligned with like 2.4% of Lancer players. The rest use D&D style diagonals cost 1.5, round down. One, two-three, four, five-six etc.
EDIT: Repeating my comment above because I don't agree with your interpretation of the game rules. They only allow diagonal distortion on movement, not attack range.
-Pg 64 RAW, range is range. So get out your ruler. Diagonals are only mentioned in regards to *movement* pg 62.-
EDIT2: Also, you don't need to use hexagons. You can use the Midpoint Circle Algorithm and keep a grid. Here's godot-rgmap on github looks to have already implemented what you'll need so you can crib the code (MIT license) https://github.com/alex-karev/godot-rgmap and a youtube link