PHP, 84 Bytes

<?=preg_replace(["#[a-z]#i","#(?<!l)l#","#(?<=l)l#","#e(?!e)#"],[l,B,e,t],$argv[1]);

PHP ,117 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,-1+$l=strlen($m[0]),e).t,0,$l);},$argv[1]);

PHP, 84 Bytes

<?=preg_replace(["#[a-z]#i","#(?<!l)l#","#(?<=l)l#","#e(?!e)#"],[l,B,e,t],$argv[1]);

PHP, 117 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,-1+$l=strlen($m[0]),e).t,0,$l);},$argv[1]);

PHP, 77 Bytes

<?=preg_replace(["#[a-z]#i","#\bl#","#(?<=l)l#","#e\b#"],[l,B,e,t],$argv[1]);

PHP ,117 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,-1+$l=strlen($m[0]),e).t,0,$l);},$argv[1]);

PHP, 84 Bytes

<?=preg_replace(["#[a-z]#i","#(?<!l)l#","#(?<=l)l#","#e(?!e)#"],[l,B,e,t],$argv[1]);

PHP ,117 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,-1+$l=strlen($m[0]),e).t,0,$l);},$argv[1]);

PHP  ,119 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,($l=strlen($m[0]))-1,e).t,0,$l);},$argv[1]);

PHP, 77 Bytes

<?=preg_replace(["#[a-z]#i","#\bl#","#(?<=l)l#","#e\b#"],[l,B,e,t],$argv[1]);

PHP ,117 Bytes

<?=preg_replace_callback("#[a-z]+#i",function($m){return substr(str_pad(Bl,-1+$l=strlen($m[0]),e).t,0,$l);},$argv[1]);