It’d be really nice and probably more realistic to move the number of valves and inclusion of VVL to the variant rather than the family.
Prior to DOHC 4V engines becoming ubiquitous it was pretty common for engines with long lineages (or even much less long) to be in the same family with varying numbers of valves. the more well known examples are probably the Ford modular V8 came in both single cam and twin cam varieties with valve counts from 2 to 4, as well as the various “quattrovalvole” models out of italy. Just picking the placement of the camshaft (block or head) might be the most freeing way of doing things and doesn’t allow for anything unheard of.
Would also be really nice to be able to base one family of engines off another, possibly with engineering time bonus/penalties depending on how similar the two are so you could, for example, cut a V8 in half to make an inline 4 or make a V12 from two V6s. This could possibly also accomplish the former as it isn’t very common to switch to fewer valves per cylinder, although Mercedes actually did for a bit in the early aughts.
Own little thing: For V10s, it would be nice to have the option of either odd or even firing crankshafts, basically like flat vs cross plane for V8s.
At the moment, particularly for single bank engines, throttle bodies have a giant jump from single to per cylinder. I recall a dev update on the subject of more options for induction, is that still being worked on? If it isn’t, a quick and dirty way reducing this jump might be to add a “big single” option of some sort.