featuring elements of two or more gamemodes
Do you mean maps where you play multiple different gamemodes in order to complete a run (e.g. stage 1 is RJ and stage 2 is SJ)? If so that functionality isn't possible yet as changing gamemode requires reloading the map and I don't think that's planned to change any time soon (before 2.0.0), if ever.
Doing a full game run of the campaign once that is finished would include playing multiple gamemodes as you need to finish every section* (surf, bhop, rj, sj) and once we are closer to adding that system it could an idea to allow mappers to make their own campaigns if they wanted to make enough maps to support it, each being a different gamemode. There is also the "playlist" functionality (https://github.com/momentum-mod/game/issues/818) where people can potentially run a list of maps in order, also obviously supporting playing a surf map and then a bhop map and etc.
*a section here means an individual campaign. there will be 4 campaigns, 1 per the main 4 gamemodes I listed above. each campaign will involve playing a bunch of maps in sequential order. a "full game" speedrun then is just playing all 4 campaigns back to back