My favourite is to use JGR Patch Pack, where, besides of other settings such realistic breakdown and repair payment (these both make together requirement of good servicing, but without frequently and annoying long stops), possibility of increasing max loan up to 5000000 GPB.
Such high initial loan give possibility to increase price of vehicles and constructions by means of Base Cost grfs. Unlike normal openttd, where you must just look for gap between vehicle income and running costs, in such case you must also mind interest rates.
My experimental openTTD server: 220.127.116.11:3979 non-standard client, now testing: JGRPP http://tiny.pl/ggnch
Projects: Reproducible Map Generation patch
, NewGRFs: Manpower industries, PolTrams, Polroad, 600mm narrow gauge, preindustrial houses, wired, ECS industry extension.