One of the homebrews I am making is a Pokemon homebrew, but the source material uses a 1-100 Level System. As you know, 5e stops leveling at 20. Of course, the obvious solution is to just divide all level-related things from Pokemon by 5 to make the two fit, rounding when necessary, but this creates some issues. Of course, I don't want to make 5e adapt the 1-100 system, either. If I did, I'd be bound to break the Bounded Accuracy of the game. As a DM, house-ruling and minor aspects of home-brewing is pretty basic stuff, but this seems to be more difficult since the choice would have a wider influence than making a pack of Lesser Werewolves or allowing a non-specific Wisdom (Perception) check as an Interaction.
Would my proposed method of making a L100 and 5e's L20 systems fit work optimally or would it cause me serious problems?
Overview of Mechanics
The idea I am toying with is creating a sub-level [Leveling System] exclusively for Pokemon, thus still allowing them to go to Level 100 (following their normal XP/Leveling system from the Pokemon franchise) and having everything else cap at 20 (using 5e's standard XP/Leveling system), while still confining a Pokemon's stat growth to something similar to the 5e system as if their Levels were [Pokemon Level]/5, to maintain balance.
Example: PC Bernard is a Level 3 Paladin. He has a Level 16 Onix. While Onix will display "Level 16" to the other PCs, its stats are the equivalence of a Level 3 PC/NPC within the 5e system. It gains experience following its experience track in the Pokemon games and gains new attacks according to its Pokemon Level, but its proficiencies and gradual stat increases approximately resemble its equivalent 5e level (in this case, "16/5": round down to "3", even if .5 or more). If Onix levels up to Level 20, it will be about the equivalence of a 5e Level 4 PC. (Obvious issue here being wild encounter balancing to make encounters of player party vs. Pokemon an actual challenge.)
I don't know if this would work or if it would break the system in that stats are a little more frequent increases and the their access to a wider array of attacks that the PCs would be able to benefit from early on in a campaign. I've been looking at this too long and need a fresh set of eyes to tell me if this idea is functional or if I need to scrap it.
My intended goals for this change are that it 1) functions, 2) has minimal impact on other aspects of 5e's system, and 3) prevents a Level 5 Pokemon from being a murder machine capable of killing off a Level 1 PC without the system/DM having to enforce an exclusively Pokemon vs. Pokemon battle system that must be strictly adhered to (I want the idea of players vs. Pokemon to be a possible plot that I or others could play around with). These three aspects seem to be mandatory to get a conversion/assimilation to work.
The idea is to make Pokemon be creatures within the world, much like familiars, animals, and monsters. For a "Mystery Dungeon" campaign, where players are Pokemon, I would probably create a different module seeing as there are many stark differences between the two Pokemon systems. This is so you better understand what it is I am trying to do.