Bay 12 Games Forum

For many small biomes you could have a look at what I did here http://www.bay12forums.com/smf/index.php?topic=158646.msg7324834#msg7324834.  Then adapt to your needs.  Beware that this will have basically no lakes/seas (will need water edges as recommended a couple of posts following, or decreasing min elevation below 100 depending on preference).  It also generates pretty deep embarks generally (levels_above... settings). You might also play with the temperature min/max as I was finessing that for precisely what I liked. 

A great resource if you haven't found it already is http://dwarffortresswiki.org/index.php/DF2014:Advanced_world_generation.

It is trivially easy to increase megabeast/titan/semi-mb numbers.  Similarly with civiliations. (Though kobolds and caves go together, don't leave them out in the cold, particularly with extra mb's.) Mineral scarcity=100 gives you more ores than you will ever use... a lot/most embarks will have iron.  It's the towers that will be the tricky part that I can't help with but generally long histories and lots of civ's for conflicts are recommended.  Maybe increasing the evil square count as well, I dunno?  There are a couple of threads that will pop by searching the forum that will be useful, including recently.

I remember seeing some reddit threads (at an earlier date) with some misleading information/assumptions.  Particularly what springs to mind is increasing the subregion count to 20000.  The game caps this at 5000 and increasing it beyond this limit has no effect.  But best to confirm this in practice for yourself as you play with the other variations.

For quickly testing your parameter sets for geography keep the history to the minimum of 2 years to make things go much quicker.  Tweak regenerate, tweak regenerate, until you are pretty consistently getting geographies you like then go for the real ones with longer histories that might get played.  If you find a map with a geography you particularly like it is possible to regenerate it with the main seed but a different history seed for somewhat different (locations can be limited) civilization distribution.  I assume with enough repetitions you might get towers occasionally in desired spots? Best of luck.

If you change the world's geography, you may change everything that comes after it - pre-set values constrain this, but even the smallest changes I've seen has moved rivers at least 5 local map tiles, with usual effect being erasing their existence entirely in favour of different ones. However, it doesn't seem to always change things - I've increased elevation in one place without it affecting rivers in another place sometimes.

Changing parameter can change the geography to eradicate features completely (including making world where no dorfs can exist). Thus, the amount of change to site abundance is dependent on which parameters you change and how.

Added a parameter "megas" check into the above script without which it excludes megabeasts and procedurals, then confirmed adding ogres to gobbos when used before their placement during world gen.

Toady recently said the next release will overshoot the one year mark of the previous one slightly (July 5:th). This probably means the next release will appear in the latter half of July or in August (no promises, though). However, if you are dependent upon tools such as DFHack or DT on the LNP (containing the others), and possibly also tile sets, it will take some time for those to catch up, probably a month or two (although DT is a bit iffy, since there is currently nobody who maintains it officially).